Exhibit 10.71

# SEVENTH AMENDMENT TOAGREEMENT OF SALE AND
PURCHASE

THIS
SEVENTH AMENDMENT TO AGREEMENT OF SALE AND PURCHASE (this Seventh
Amendment) is entered into as of the 28th day of October,
2004, by and between MACK-CALI TEXAS PROPERTY L.P., a Texas limited partnership
(Seller), and CENTENNIAL ACQUISITION COMPANY, a Texas
corporation, and WARAMAUG ACQUISITION CORP., a Texas corporation (collectively,
Purchaser).

A.              Seller
and Purchaser entered into that certain Agreement of Sale and Purchase           dated as
of August 10, 2004, as amended by that certain Amendment to Agreement           of Sale
and Purchase between Seller and Purchaser dated as of October 12, 2004,           as
further amended by that certain Second Amendment to Agreement of Sale and
          Purchase between Seller and Purchaser dated as of October 18, 2004, as further
          amended by that certain Third Amendment to Agreement of Sale and Purchase
          between Seller and Purchaser dated as of October 20, 2004, as further
          amended by that certain Fourth Amendment to Agreement of Sale and Purchase
          between Seller and Purchaser dated as of October 21, 2004, as further
          amended by that certain Fifth Amendment to Agreement of Sale and Purchase
          between Seller and Purchaser dated as of October 25, 2004, and as further
          amended by that certain Sixth Amendment to Agreement of Sale and Purchase
          between Seller and Purchaser dated as of October 27, 2004 (as amended to
          date, the Purchase Agreement). All capitalized
          terms used but not defined herein shall have the meaning given to such terms in
          the Purchase Agreement.

B.              Seller
and Purchaser now desire to amend the Purchase Agreement as set forth           below.

NOW,
THEREFORE, for good and valuable consideration, the receipt and sufficiency of which is
hereby acknowledged, Seller and Purchaser agree as follows:

1.    Definitions.

| | (a)              The
following definitions are hereby added to Section 1.1 of the Purchase
          Agreement:
| | ---------------------------------------------------------------------------------------------------------------

| | Adjacent
Parcel means that certain 3.9498-acre real property parcel known as
Lot 3, Block 9, of Replat of Lots 2&3, Block 9, Corporate Square Third
Installment, an Addition to the City of Richardson, Dallas County, Texas, according to
the map or plat thereof recorded in Volume 86010, Page 818, of the Map Records
of Dallas County, Texas.
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Adjacent
Parcel Outside Acquisition Date means March 31, 2005, provided
that Seller may, by providing written notice to Purchaser no later than March 28, 2005,
extend the Adjacent Parcel Outside Acquisition Date up to thirty (30) days.
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Parking
Easement has the meaning set forth in Section 2(a) of the
Seventh Amendment.
| | ----------------------------------------------------------------------------------------

---

| | (b)              The
definitions of Closing, Closing Date,          Project, Real
Property, and Scheduled Closing           Date are hereby deleted from
Section 1.1 of the Purchase Agreement in           their entirety and replaced with
the following:
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Closing
means the consummation of the purchase and sale of the Century Property and the Tri West
Property, on the one hand, or the Santa Fe Property and the Adjacent Parcel (or Parking
Easement, if applicable) on the other hand, as applicable, as provided for in
Article X of the Purchase Agreement.
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Closing
Date means the date on which the Closing of the Century Property and
the Tri West Property, on the one hand, or the Santa Fe Property and the Adjacent Parcel
(or Parking Easement, if applicable), on the other hand, as applicable, actually
occurs.
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Project
means that portion of the Property located on and used exclusively in connection with the
Century Property, the Tri West Property or, collectively, the Santa Fe Property and either
the Adjacent Parcel or the Parking Easement.
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Real
Property means that certain parcel or parcels of real property
located at 84 N.E. Loop 410, San Antonio, Texas; 1122 North Alma Road, Richardson, Texas;
and 3030 LBJ Freeway, Dallas, Texas, as more particularly described on the legal
descriptions attached to and made a part of the Purchase Agreement respectively as
Exhibit D-1, Exhibit D-2 and
Exhibit D-3, together with the Adjacent Parcel (or Parking
Easement, if applicable), and together with all of Sellers right, title and
interest, if any, in and to the appurtenances pertaining thereto, including but not
limited to Sellers right, title and interest in and to the adjacent streets, alleys
and right-of-ways, and any easement rights, air rights, subsurface development rights and
water rights.
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Scheduled
Closing Date means, (i) with respect to the Century Property and
the Tri West Property, November 23, 2004, and (ii) with respect to the Santa Fe
Property and the Adjacent Parcel (or Parking Easement, if applicable), the Adjacent Parcel
Outside Acquisition Date (as extended, if applicable), subject to Section 2(f) of the
Seventh Amendment.
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2.    Purchase
of Adjacent Parcel; Parking Easement.

| | (a)              Seller
shall make commercially reasonable efforts to acquire either (i) fee           title
to the Adjacent Parcel or (ii) a perpetual, appurtenant easement over           all
or a portion of the Adjacent Parcel for the exclusive use of all of the           current
parking spaces located on the Adjacent Parcel (the Parking           Easement),
in either case on or before the Adjacent Parcel           Outside Acquisition Date from
the current owner thereof           (MCI) and, on the
Closing Date pertaining to           the Santa Fe Property, transfer the Adjacent Parcel
or, if applicable, Parking           Easement, to Purchaser, provided that Seller may, at
its option, direct that the           deed of the Adjacent Parcel or the instrument
creating the Parking Easement be           from MCI directly to Purchaser, effective as
of the date of the Closing of the           sale of the Santa Fe Property to Purchaser.
If Seller is able to do so, Seller           and Purchaser shall proceed to Closing with
respect to the Santa Fe Property and           the Adjacent Parcel (or Parking Easement,
if applicable) on the Scheduled           Closing Date and the Earnest Money Deposit then
in escrow, together with all           interest accrued thereon, will be applied at such
Closing to the Purchase Price           attributable to the Santa Fe Property and, if
applicable, the Adjacent Parcel.
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2

---

| | (b)              Purchaser
shall have the right to review any proposed purchase agreement between           Seller
and MCI and to make comments to Seller regarding the same promptly after
          receipt of a draft thereof from Seller, provided that, other than           (i) confirming
that such purchase agreement allows for a due diligence           period that extends no
less than the longer of (A) ten (10) Business Days           after the receipt of a
current title commitment, related exception documents and           current survey of the
Adjacent Parcel (or area covered by the Parking Easement,           if applicable) and (B) thirty
(30) days after the date of the purchase           agreement with MCI, with the right to
conduct a Phase II environmental site           assessment if Purchaser reasonably
determines that a Phase II environmental site           assessment is required and to
extend the due diligence period by an additional           fifteen (15) days, if
necessary, in order to conduct such Phase II           environmental site
assessment, and (ii) addressing title and survey costs           as set forth in
Section 2(e)(i) of this Seventh Amendment, the Closing Date           as set forth
in Section 2(f) of this Seventh Amendment and Purchasers           right to
conduct due diligence as set forth in Section 2(e)(ii) of this           Seventh
Amendment, Seller is under no obligation to incorporate or attempt to
          incorporate any such comments into any revisions to such purchase agreement.
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (c)              In
the event that neither fee title to the Adjacent Parcel nor a Parking           Easement
is acquired by Seller by the Adjacent Parcel Outside Acquisition Date           (or
Seller has not acquired the right to direct the deed of the Adjacent Parcel           or
the instrument conveying the Parking Easement directly from MCI to Purchaser           on
or before the Adjacent Parcel Outside Acquisition Date), Seller will not be           in
default under the Purchase Agreement and (i) Seller and Purchaser shall
          proceed to Closing on the Santa Fe Property only on the Scheduled Closing Date,
          (ii) the Earnest Money Deposit then in escrow, together with all interest
          accrued thereon, will be applied to the Purchase Price attributable to the
Santa           Fe Property, (iii) the Purchase Agreement will terminate with
respect to           the Adjacent Parcel and the Parking Easement, and except with
respect to the           Termination Surviving Obligations applicable to the Adjacent
Parcel and the           Parking Easement, the Purchase Agreement shall be null and void
with respect to           the Adjacent Parcel and Parking Easement and the parties shall
have no further           obligation to each other with respect thereto, and (iv) Purchaser
shall           receive a credit of Five Hundred Fifty Thousand and No/100 Dollars
($550,000.00)           toward the Purchase Price of the Santa Fe Property.
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (d)              If
an agreement with MCI to purchase the Adjacent Parcel cannot be reached and           MCI
is willing to grant the Parking Easement only if the Parking Easement covers
          more property than is necessary for the use of the parking spaces currently
          located on the Adjacent Parcel, then Seller shall notify Purchaser promptly
upon           such determination and Purchaser shall, within three (3) Business Days
after           receipt of such notification, notify Seller whether Purchaser is willing
to           accept the Parking Easement as proposed by MCI. If Purchaser elects (or is
          deemed to have elected) to accept the Parking Easement as proposed by MCI, then
          Purchaser and Seller shall proceed to Closing on the Santa Fe Property and the
          Parking Easement as set forth in Section 2(a) of this Seventh Amendment.
In           the event that Purchaser elects not to accept such Parking Easement, then
Seller           will not be in default under the Purchase Agreement and (i) Seller
and           Purchaser shall proceed to Closing on the Santa Fe Property only on the
          Scheduled Closing Date, (ii) the Earnest Money Deposit then in escrow,
          together with all interest accrued thereon, will be applied to the Purchase
          Price attributable to the Santa Fe Property, (iii) the Purchase Agreement
          will terminate with respect to the Adjacent Parcel and the Parking Easement,
and           except with respect to the Termination Surviving Obligations applicable to
the           Adjacent Parcel and the Parking Easement, the Purchase Agreement shall be
null           and void with respect to the Adjacent Parcel and Parking Easement and the
          parties shall have no further obligation to each other with respect thereto. If
          Purchaser does not respond to Sellers notice within the time period set
          forth above in this Section 2(d), then Purchaser will be deemed to have
          elected to accept the Parking Easement as proposed by MCI.
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3

---

| | (e)     With
respect to due diligence investigation by Purchaser of the Adjacent Parcel,
          Seller and Purchaser agree as follows:
| | -----------------------------------------------------------------------------------------------------------------------------------------

| | (i)    Seller
shall have no obligation to provide any title commitment, title policy,           survey,
environmental reports, tax or utility bills, or any other due diligence           items
to Purchaser relating to or covering the Adjacent Parcel. To the extent
          Purchaser desires to obtain a title commitment, title policy or survey of the
          Adjacent Parcel or to obtain any other reports or conduct any other
          investigations of the Adjacent Parcel, all of such items and investigations
          shall be at Purchasers sole cost and expense (provided that Seller shall
          use commercially reasonable efforts to obtain an agreement with MCI that the
          costs of a survey of the Adjacent Parcel (or Parking Easement) and the owner
          policy of title insurance issued in connection with the purchase of the
Adjacent           Parcel (or the Parking Easement) from MCI will be paid by MCI), and
any such           reports shall be addressed to or for the benefit of Seller in addition
to           Purchaser.
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (ii)    Purchasers
right to conduct such due diligence investigations of the           Adjacent Parcel shall
be solely to the extent permitted under the future           purchase agreement between
Seller and MCI, provided that Seller will require in           the negotiations of such
purchase agreement that Purchaser be permitted (as           Sellers designee,
agent or otherwise) to conduct such due diligence as is           customary for a
transaction of the type contemplated by such purchase agreement           and otherwise
in accordance with Section 2(b)(i) of this Seventh Amendment.           In the event
such purchase agreement does not permit Purchaser to conduct such           due diligence
as aforesaid, Seller shall not be in default under the Purchase           Agreement, and
Seller and Purchaser shall proceed to Closing on the Santa Fe           Property as set
forth in Section 2(c).
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (iii)    Purchaser
may request that Seller terminate the purchase agreement between           Seller and MCI
during the due diligence period thereunder, provided that           (A) if Purchaser
does not provide notice to Seller such that Seller has           adequate time to
terminate such purchase agreement before the expiration of the           due diligence
period contemplated thereby, Purchaser will reimburse Seller           immediately for
any earnest money deposit lost by Seller as a result of such           termination and
any other penalty suffered or incurred by Seller as a result of           such
termination, and (B) Purchaser may request that such purchase           agreement be
terminated only if Purchaser determines that all or any of the           parking spaces
currently located on the Adjacent Parcel (or, if applicable,           Parking Easement)
are not useable for parking because such use (1) is not           available because
of a failure of title to the Adjacent Parcel, or because a           restrictive
covenant, setback requirement or third partys easement rights           prohibit
such use, or (2) is not available without violating an applicable           zoning
ordinance. In addition, and subject to clause (iii)(A) of this           Section 2(e),
if an environmental problem exists on the Adjacent Parcel (or           Parking Easement,
if applicable) with respect to which a governmental agency or           other
governmental authority is reasonably likely to require remediation or that           must
be remediated in order for the Adjacent Parcel (or Parking Easement, if
          applicable) to be used for commercial purposes, then (x) if the estimated
          remediation costs are $50,000 or less, Seller and Purchaser will proceed to
          Closing on the Santa Fe Property and the Adjacent Parcel (or Parking Easement,
          if applicable) and the costs of remediation shall be borne by Purchaser;
          (y) if the estimated remediation costs are more than $50,000 but do not
          exceed $100,000, then, if Seller agrees to provide a credit at Closing toward
          the Purchase Price in the amount of such costs in excess of $50,000, Seller and
          Purchaser will proceed to Closing on the Santa Fe Property and the Adjacent
          Parcel (or Parking Easement, if applicable) and the remaining costs of
          remediation shall be borne by Purchaser and if Seller does not agree to provide
          such a credit, Purchaser may terminate the Purchase Agreement with respect to
          the Adjacent Parcel and Parking Easement and, in such event, Seller will
          terminate the purchase agreement with MCI; and (z) if the estimated
          remediation costs are more than $100,000 and Seller agrees to provide a credit
          at Closing toward the Purchase Price in the amount of $50,000, Purchaser may
          either agree to be responsible for the remediation costs up to $50,000 and in
          excess of $100,000 and proceed to Closing on the Santa Fe Property and the
          Adjacent Parcel (or Parking Easement, if applicable) or terminate the Purchase
          Agreement with respect to the Adjacent Parcel and Parking Easement, in which
          event Seller will terminate the purchase agreement with MCI, and if Seller does
          not agree to provide a credit at Closing toward the Purchase Price in the
amount           of $50,000, Purchaser may terminate the Purchase Agreement with respect
to the           Adjacent Parcel and Parking Easement, in which event Seller will
terminate the           purchase agreement with MCI. All such costs of remediation shall
be based on the           reasonable, good faith estimate of Seller and Purchaser. In the
event of a           termination of the Purchase Agreement with respect to the Adjacent
Parcel (or           Parking Easement) pursuant to this clause (iii) of Section 2(e),
          Seller and Purchaser shall proceed to Closing on the Santa Fe Property as set
          forth in Section 2(c).
| | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

4

---

| | (iv)    If
the Purchase Agreement is terminated with respect to the Adjacent Parcel and
          Parking Easement pursuant to Section 2(e)(iii) of this Seventh Amendment
as           a result of an environmental problem, then if Purchaser or an affiliate of
          Purchaser obtains fee title to, a lease of or parking easement rights over all
          or any part of the Adjacent Parcel at any time before the date that is the
          earlier of (A) three (3) years after the Closing Date of the Santa Fe
          Property and (B) the date on which the Santa Fe Property is transferred to
          a third party who is not an affiliate of Purchaser, Purchaser will immediately
          remit to Seller the $550,000 credit provided for in Section 2(c);
provided,           however, if the remediation costs exceed $50,000, Purchaser shall
receive a           credit against the $550,000 in the amount of such excess, up to a
maximum credit           of $50,000. For the purposes of this paragraph, an affiliate of
          Purchaser means any person or entity in which Purchaser, Steven H. Levin, Paul
          Nussbaum, The Praedium Fund V, LP and/or any entity controlling, controlled by
          or under common control with any of them has any equity interest or management
          rights. If the deed to the Santa Fe Property is not directed to an unaffiliated
          third party at Closing, then the deed to Purchaser or its affiliate at Closing
          will contain a provision that conforms to the provisions set forth in this
          paragraph. The provisions of this clause (iv) shall survive Closing.
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (v)    Notwithstanding
the foregoing, in the event that Purchasers due diligence           investigations
with respect to the Adjacent Parcel reveal that, as a result of           (A) a
failure of title, a restrictive covenant, a setback requirement or           third-party
easement rights and/or (B) an applicable zoning restriction,           Purchaser
will not, after acquisition of fee title to the Adjacent Parcel, be           able to add
a minimum of sixty-seven (67) new parking spaces to the Adjacent           Parcel, then
Purchaser will receive a credit toward the Purchase Price of the           Adjacent
Parcel in an amount equal to Five Thousand and No/100 Dollars           ($5,000.00) for
every such additional parking space, up to 67 such additional           parking spaces,
that Purchaser will not be able to add to the Adjacent Parcel,           and Seller and
Purchaser shall proceed to Closing on the Santa Fe Property and           the Adjacent
Parcel as set forth in Section 2(a) of this Seventh Amendment.
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

5

---

| | (f)    Seller
will use commercially reasonable efforts to ensure that the purchase           agreement
pertaining to the Adjacent Parcel (or Parking Easement) allows for the           Closing
on the Adjacent Parcel (or Parking Easement) to occur no sooner than           March 31,
2005, and if such purchase agreement so provides, the Closing           Date for the
Santa Fe Property and the Adjacent Parcel (or Parking Easement)           will occur no
sooner than March 31, 2005, unless Purchaser requests an           earlier Closing
Date and Seller and MCI both agree to such earlier date. If           Seller is unable,
using commercially reasonable efforts, to obtain an agreement           from MCI with
respect to the Closing Date as set forth above in this           Section 2(f), and
Seller is therefore required to take fee title to the           Adjacent Parcel or accept
the Parking Easement before the Closing of the sale by           Seller to Purchaser
thereof, then the owner policy of title insurance provided           for under the
purchase agreement with MCI will be in the name of Seller and, to           the extent
any cost therefor (including the cost of modifying the survey           exception to read
shortages in area only) is not paid by MCI, such           cost shall be
borne by Purchaser, and the cost of any subsequent owner policy of           title
insurance issued to Purchaser (or its permitted assignee or designee) with
          respect to the Adjacent Parcel or Parking Easement shall be borne by Purchaser.
          In no event will the Closing Date for the sale by Seller to Purchaser of the
          Adjacent Parcel (or Parking Easement) be different than the Closing Date for
the           sale of the Santa Fe Property to Purchaser.
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (g)    As
a condition to Purchasers obligation to close on the Santa Fe Property
          and, if and as applicable, the Adjacent Parcel or the Parking Easement,
          Purchaser shall have arranged for an affiliate of Seller or for an unaffiliated
          third party to provide a loan to Purchaser substantially on the terms set forth
          on Exhibit Aattached to this Seventh Amendment. In
          the event such loan is not available on the Scheduled Closing Date for the
Santa           Fe Property (and, if applicable, Adjacent Parcel or Parking Easement),
the           Earnest Money Deposit then in escrow, together with all interest accrued
          thereon, will be returned to Purchaser, this Agreement will terminate with
          respect to the Santa Fe Property, the Adjacent Parcel and the Parking Easement,
          and except with respect to the Termination Surviving Obligations applicable
          thereto, the Purchase Agreement shall be null and void with respect to the
Santa           Fe Property, the Adjacent Parcel and the Parking Easement, and the
parties shall           have no further obligation to each other with respect thereto,
provided that,           notwithstanding the foregoing, if such loan is not available
because           (i) Purchaser is in default under the Purchase Agreement and/or
          (ii) Purchaser has failed to satisfy any conditions to funding of the loan
          as set forth in the relevant loan commitment, then Seller shall have the
          remedies set forth in Section 13.2 of the Purchase Agreement.
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3.    Purchase
Price.

| | (a)    In
the event that Seller causes fee title to the Adjacent Parcel to be           transferred
to Purchaser (or its permitted assignee or designee) at Closing, the           Purchase
Price shall be increased to Forty-One Million Nine Hundred Eighty-Five           Thousand
and No/100 Dollars ($41,985,000.00).
| | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (b)    Section
3.1 of the Purchase Agreement is revised to reallocate the Purchase           Price as
follows:
| | --------------------------------------------------------------------------------------------------------------

6

---

|                                 | 
|-------------------------------- | 
|Century Property                 | 
|                                
|Tri West Property                | 
|                                
|Santa Fe Property                | 
|                                
|Adjacent Parcel (if applicable)  | 
|                                
|Parking Easement (if applicable) | 

4.    Earnest
Money Deposit.

| | (a)    Section
4.1(a) of the Purchase Agreement is hereby revised as follows:
| | -----------------------------------------------------------------------------

| | (i)    No
later than 5:00 p.m. Eastern Time on October 29, 2004, Purchaser shall           deposit
an additional earnest money deposit in the amount of Three Hundred           Seventy-Five
Thousand and No/100 Dollars ($375,000.00) on account of the           Purchase Price for
the Tri West Property and the Century Property with Escrow           Agent, and such
additional earnest money will, upon deposit, become part of the           Earnest Money
Deposit.
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (ii)    No
later than 5:00 p.m. Eastern Time on October 29, 2004, Purchaser shall
          deposit an additional earnest money deposit in the amount of Three Hundred
          Thousand and No/100 Dollars ($300,000.00) on account of the Purchase Price for
          the Santa Fe Property and the Adjacent Parcel with Escrow Agent, and such
          additional earnest money will, upon deposit, become part of the Earnest Money
          Deposit.
| | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (iii)    The
Earnest Money Deposit shall be allocated and credited to the Purchase Price
          paid at the relevant Closings as follows (with any accrued interest
          proportionally allocated):
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|                                | 
|------------------------------- | 
|Century Property                | 
|                                | 
|Tri West Property               | 
|                                | 
|Santa Fe Property and, if       | 
|applicable, the Adjacent Parcel | 

| | (iv)    In
the event that the additional Earnest Money Deposit in the amount of
          $375,000.00 and the additional Earnest Money Deposit in the amount of
          $300,000.00 are not deposited by 5:00 p.m. Eastern Time on October 29, 2004,
          then the Purchase Agreement shall automatically terminate, the Escrow Agent
will           promptly return to Purchaser all monies deposited toward the Earnest Money
          Deposit through such deadline, without interest, and except with respect to the
          Termination Surviving Obligations, this Agreement shall be null and void and
the           parties shall have no further obligations to each other.
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

7

---

5.    Evaluation
Period and Title and Survey Review Period. The           parties
acknowledge and agree that the Evaluation Period has expired and that           all time
periods for the review of title and survey matters relating to the           Century
Property, Tri West Property and Santa Fe Property have expired.           Notwithstanding
any right Purchaser may have to conduct due diligence           investigations with
respect to the Adjacent Parcel or Parking Easement as set           forth above in Section 2(e)
of this Seventh Amendment, Purchaser shall have           no right to terminate the
Purchase Agreement with respect to the Tri West           Property, Century Property or
Santa Fe Property solely as a result of any           matters discovered during such due
diligence investigations.

6.    Additional
Adjacent Parcel Matters.

| | (a)    The
provisions of Section 7.1 of the Purchase Agreement shall not apply to           the
Adjacent Parcel (or Parking Easement) until such time as Seller acquires it.
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (b)    None
of the representations of Seller set forth in the Purchase Agreement (other
          than those set forth in Section 8.1(a), (b), (c), (e), (k) and (l) of the
          Purchase Agreement, to the extent applicable) shall apply to the Adjacent
Parcel           (or Parking Easement).
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (c)    The
form of Consulting Agreement attached as Exhibit R          to
the Purchase Agreement will be revised as follows:
| | ----------------------------------------------------------------------------------------------------------------------------

| | (i)    if
either fee title to the Adjacent Parcel is purchased or the Parking Easement           is
obtained by Purchaser as contemplated hereby, to delete the Re          line
thereof in its entirety and to replace it with the following:
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | Consulting
Agreement  Leasing/sale of that certain real property located at 1122 North Alma
Road, Richardson, Texas, and [describe Adjacent Parcel or Parking Easement,as
applicable] (collectively, the Santa Fe Property)"; and
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (ii)    if
fee title to the Adjacent Parcel is purchased by Purchaser as contemplated
          hereby, to delete $2,350,000 from the second sentence of
          paragraph 3 of the Consulting Agreement and replace it with
          $2,885,000, unless any credits toward the Purchase Price are made
          pursuant to Section 2(e)(v) of this Seventh Amendment, in which case
          $2,350,000 will be replaced by an amount equal to $2,885,000 less
          the aggregate amount of any such credits.
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | If,
ultimately, neither the Adjacent Parcel is purchased nor the Parking Easement obtained by
Purchaser in accordance with the provisions of this Seventh Amendment, then the changes to
the form of Consulting Agreement set forth above in this Section 6(c) will not be
made and clauses (i) and (ii) of this Section 6(c) shall be null and void. In
such event, if the credit set forth in Section 2(c)(iv) of this Seventh Amendment
applies, then $2,350,000 will be deleted from the second sentence of
paragraph 3 of the Consulting Agreement and replaced with $1,800,000.
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

7.    Estoppels.
The words twenty (20) days in the           first sentence of Section 7.2
of the Purchase Agreement are hereby deleted           and replaced with the words thirty
(30) days.

8

---

8.    Notices.
The telephone and facsimile numbers of Steven H.           Levin are hereby revised as
follows:

| | Telephone:
(972) 407-0104        Facsimile: (972) 733-0782
| | ----------------------------------------------------------

9.    Assignment.
Section 15.1 of the Purchase Agreement is           hereby deleted in its entirety and
replaced with the following:

Assignment;
Binding Effect. Purchaser shall have a one-time right to assign this
Agreement to, (a) with respect to the Century Property and the Tri West Property,
one or more entities (but no more than two entities per Project) in which Paul Nussbaum
and Steven H. Levin, together or either of them individually, own, directly or
indirectly, any portion of the equity interest, provided that The Praedium Fund V, LP or
a wholly-owned subsidiary thereof is the controlling investor in such assignee(s) and
Purchaser provides notice of such assignment to Seller at least five (5) Business Days
prior to the Closing Date, which notice shall include evidence that the assignment
complies with the requirements of this Section 15.1, and (b) with respect to
the Santa Fe Property and, if applicable, the Adjacent Parcel (or Parking Easement), any
person or entity so long as Purchaser provides notice of such assignment to Seller at
least five (5) Business Days prior to the Closing Date, and if Purchaser so elects, the
Deed of the Santa Fe Property and, if applicable, the Adjacent Parcel (or, if applicable,
the instrument creating the Parking Easement) will be directly to the person or entity
identified by Purchaser. Purchaser will not otherwise have the right to assign this
Agreement without Sellers prior written consent. No assignment of this Agreement by
Purchaser shall relieve Purchaser of its obligations hereunder.

10.    Reaffirmation.
Except as modified by this Seventh           Amendment, the Purchase Agreement is hereby
ratified and confirmed and in full           force and effect. In the event of a conflict
between the terms of this Seventh           Amendment and the Purchase Agreement, the
terms of this Seventh Amendment shall           control.

11.    Counterparts.
This Seventh Amendment may be executed in any           number of counterparts, all of
which taken together will constitute one and the           same Seventh Amendment, and
the signature page of any counterpart may be removed           therefrom and attached to
any other counterpart. This Seventh Amendment shall be           legally binding upon
receipt by each party of the facsimile or the original           signature of Seller and
of Purchaser.

[SIGNATURES
FOLLOW ON NEXT SUCCEEDING PAGE]

9

---

IN
WITNESS WHEREOF the parties have executed this Seventh Amendment as of the day and year
first above written.

| |  | PURCHASER:CENTENNIAL ACQUISITION COMPANYBy:  /s/ Steven H. Levin
Name:  Steven H. LevinTitle:  President
| |  | ----------------------------------------------------------------------------------------------------------------------

| |  | WARAMAUG ACQUISITION CORP.By:  /s/  Cindy Nelson
Name:  Cindy NelsonTitle:  Vice President
| |  | --------------------------------------------------------------------------------------------------------

| |  | SELLER:MACK-CALI TEXAS PROPERTY L.P.By:  Mack-Cali Sub XVII, Inc., its general partner
      By:  /s/  Roger W. Thomas            Name:  Roger W. Thomas
      Title:  Executive Vice President                   and General Counsel
| |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

S-1

---

Exhibit A

Loan Terms

|                | 
|--------------- | 
|Loan Amount:    | 
|                | 
|                | 
|Interest Rate:  | 
|                | 
|                | 
|Loan Term:      | 
|                | 
|Payments:       | 
|                | 
|                | 
|Loan Documents: | 
|                | 
|                | 
|                | 
|                | 
|Miscellaneous:  | 
|                | 
|                | 
|                | 
|                | 
|                | 

---