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                                                                     Exhibit 4.b


                                                             Executed in 6 Parts
                                                             Counterpart No. ( )


                              NATIONAL EQUITY TRUST

                            TOP TEN PORTFOLIO SERIES 24

                            REFERENCE TRUST AGREEMENT


            This Reference Trust Agreement dated June 28, 2000 among Prudential
Securities Incorporated, as Depositor and The Chase Manhattan Bank, as Trustee,
sets forth certain provisions in full and incorporates other provisions by
reference to the document entitled "National Equity Trust Low Five Portfolio
Series, Trust Indenture and Agreement" (the "Basic Agreement") dated April 25,
1995. Such provisions as are set forth in full herein and such provisions as are
incorporated by reference constitute a single instrument (the "Indenture").


                                  WITNESSETH THAT:
                                  ---------------


            In consideration of the premises and of the mutual agreements herein
contained, the Depositor and the Trustee agree as follows:

                                     Part I.


                     STANDARD TERMS AND CONDITIONS OF TRUST


            Subject to the provisions of Part II hereof, all the provisions
contained in the Basic Agreement are herein incorporated by reference in their
entirety and shall be deemed to be a part of this instrument as fully and to the
same extent as though said provisions had been set forth in full in this
instrument except that the Basic Agreement is hereby amended in the following
manner:


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A.       Article I, entitled "Definitions", paragraph 22, shall be amended as
         follows:


         "Trustee shall mean The Chase Manhattan Bank or any successor
         trustee appointed as hereinafter provided."


B.       Article II, entitled "Deposit of Securities; Acceptance of Trust",
         shall be amended as follows:


         The second sentence of Section 2.03 Issue of Units shall be
         amended by deleting the words "on any day on which the
         Depositor is the only Unit Holder."


C.       Article III, entitled "Administration of Trust", shall be amended as
         follows:


         (i)      Section 3.01 Initial Costs shall be amended to substitute the
                  following language:


                           Section 3.01. Initial Cost The costs of organizing
                           the Trust and sale of the Trust Units shall, to the
                           extent of the expenses reimbursable to the Depositor
                           provided below, be borne by the Unit Holders,
                           provided, however, that, to the extent all of such
                           costs are not borne by Unit Holders, the amount of
                           such costs not borne by Unit Holders shall be borne
                           by the Depositor and, provided further, however, that
                           the liability on the part of the Depositor under this
                           section shall not include any fees or other expenses
                           incurred in connection with the administration of the
                           Trust subsequent to the deposit referred to in
                           Section 2.01. Upon notification from the Depositor
                           that the primary offering period is concluded, the
                           Trustee shall withdraw from the Account or Accounts
                           specified in the Prospectus or, if no Account is
                           therein specified, from the Principal Account, and
                           pay to the Depositor the Depositor's reimbursable
                           expenses of organizing the Trust and sale of the
                           Trust Units in an amount certified to the Trustee by
                           the Depositor. If the balance of the Principal
                           Account is insufficient to make such withdrawal, the
                           Trustee shall, as directed by the Depositor, sell
                           Securities identified by the

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                           Depositor, or distribute to the Depositor Securities
                           having a value, as determined under Section 4.01 as
                           of the date of distribution, sufficient for such
                           reimbursement. The reimbursement provided for in this
                           section shall be for the account of the Unitholders
                           of record at the conclusion of the primary offering
                           period and shall not be reflected in the computation
                           of the Unit Value prior thereto. As used herein, the
                           Depositor's reimbursable expenses of organizing the
                           Trust and sale of the Trust Units shall include the
                           cost of the initial preparation and typesetting of
                           the registration statement, prospectuses (including
                           preliminary prospectuses), the indenture, and other
                           documents relating to the Trust, SEC and state blue
                           sky registration fees, the cost of the initial
                           valuation of the portfolio and audit of the Trust,
                           the initial fees and expenses of the Trustee, and
                           legal and other out-of-pocket expenses related
                           thereto, but not including the expenses incurred in
                           the printing of preliminary prospectuses and
                           prospectuses, expenses incurred in the preparation
                           and printing of brochures and other advertising
                           materials and any other selling expenses. Any cash
                           which the Depositor has identified as to be used for
                           reimbursement of expenses pursuant to this Section
                           shall be reserved by the Trustee for such purpose and
                           shall not be subject to distribution or, unless the
                           Depositor otherwise directs, used for payment of
                           redemptions in excess of the per-Unit amount
                           allocable to Units tendered for redemption. As
                           directed by the Depositor, the Trustee will advance
                           funds to the Trust in an amount necessary to
                           reimburse the Depositor pursuant to this Section and
                           shall recover such advance from the sale or sales of
                           Securities at such time as the Depositor shall
                           direct, but in no event later than the termination of
                           the Trust. Repayment of any such advance shall be
                           secured by a lien on the assets of the Trust prior to
                           the interest of the Unit Holders as provided in
                           Section 6.04.

                  (ii)     The third paragraph of Section 3.05 Distribution
                           shall be amended to add the following sentence at the
                           end thereof:

                           "The Trustee shall make a special distribution of the
                           cash balance in the Income and Principal accounts
                           available for such distribution to Unit

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                           Holders of record on such dates as the Depositor
                           shall direct."

                  (iii)    The second to the last paragraph of Section 3.08 Sale
                           of Securities shall be amended to replace the word
                           "equal" with the following phrase: "be sufficient to
                           pay."

                  (iv)     Section 3.14 Deferred Sales Charge shall be amended
                           to add the following sentences at the end thereof:

                           "References to Deferred Sales Charge in this Trust
                           Indenture and Agreement shall include any Creation
                           and Development Fee indicated in the prospectus for a
                           Trust. The Creation and Development Fee shall be
                           payable on each date so designated and in an amount
                           determined as specified in the prospectus for a
                           Trust."


         D.       Reference to United States Trust Company of New York in its
                  capacity as Trustee is replaced by the Chase Manhattan Bank
                  throughout the Basic Agreement.


         E.       Section 6.05 shall be amended to delete the clause "if the
                  Depositor shall determine in good faith that there has oc-
                  curred either (1) a material deterioration in the creditwor-
                  thiness of the Trustee or (2) one or more negligent acts on
                  the part of the Trustee having a materially adverse effect,
                  either singly or in the aggregate, on the Trust or on one or
                  more Trusts, such that the replacement of the Trustee is in
                  the best interest of the Unit Holders" and insert in place
                  thereof "upon the determination of the Depositor to remove the
                  Trustee for any reason, either with or without cause,
                  including but not limited to a determination by the Deposi-
                  tor that the Trustee has materially failed to perform its
                  duties under the Indenture and the interest of Unit Holders
                  has been substantially impaired as a result".

                                    Part II.


                      SPECIAL TERMS AND CONDITIONS OF TRUST


         The following special terms and conditions are hereby agreed to:


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                  A. The Trust is denominated National Equity Trust, Top Ten
         Portfolio Series 24.

                  B. The Units of the Trust shall be subject to a deferred sales
         charge.

                  C. The contracts for the purchase of common stock listed in
         Schedule A hereto are those which, subject to the terms of this
         Indenture, have been or are to be deposited in Trust under this
         Indenture as of the date hereof.

                  D. The term "Depositor" shall mean Prudential Securities
         Incorporated.

                  E. The aggregate number of Units referred to in Sections 2.03
         and 9.01 of the Basic Agreement is 125,000 as of the date hereof.

                  F. A Unit of the Trust is hereby declared initially equal to
         1/125,000th of the Trust.

                  G. The term "First Settlement Date" shall mean July 5, 2000.

                  H. The terms "Computation Day" and "Record Date" shall mean on
         the tenth day of September 2000, December 2000, March 2001, and June
         2001.

                  I. The term "Distribution Date" shall mean on the twenty-fifth
         day of September 2000, December 2000, March 2001, and June 2001 or as
         soon thereafter as possible.

                  J. The term "Termination Date" shall mean August 2, 2001.

                  K. The Trustee's Annual Fee shall be $1.16 (per 1,000 Units)
         for 100,000,000 and above units outstanding; $1.22 (per 1,000 Units)
         for 50,000,000 - 99,999,999 units outstanding; $1.26 (per 1,000 Units)
         for 49,999,999 and below units outstanding. In calculating the
         Trustee's annual fee, the fee applicable to the number of units
         outstanding shall apply to all units outstanding.

                  L. The Depositor's Portfolio supervisory service fee shall be
         $0.25 per 1,000 Units.

               [Signatures and acknowledgments on separate pages]

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         The Schedule of Portfolio Securities in Part A of the prospectus
         included in this Registration Statement for National Equity Trust, Top
         Ten Portfolio Series 24 is hereby incorporated by reference herein as
         Schedule A hereto.