Each clearing firm is required to deposit and maintain balances in the form of cash, U. S.  government securities, certain foreign government securities, bank letters of credit or other approved investments to satisfy performance bond and guaranty fund requirements.
All non-cash deposits are marked-to-market and haircut on a daily basis.
Securities deposited by the clearing firms are not reflected in the consolidated financial statements and the clearing house does not earn any interest on these deposits.
These balances may fluctuate significantly over time due to investment choices available to clearing firms and changes in the amount of contributions required.
In addition, the rules and regulations of CBOT require that collateral be provided for delivery of physical commodities, maintenance of capital requirements and deposits on pending arbitration matters.
To satisfy these requirements, clearing firms that have accounts that trade certain CBOT products have deposited cash, U. S.  Treasury securities or letters of credit.
The clearing house marks-to-market open positions at least once a day (twice a day for futures and options contracts), and require payment from clearing firms whose positions have lost value and make payments to clearing firms whose positions have gained value.
The clearing house has the capability to mark-to-market more frequently as market conditions warrant.
Under the extremely unlikely scenario of simultaneous default by every clearing firm who has open positions with unrealized losses, the maximum exposure related to positions other than credit default and interest rate swap contracts would be one half day of changes in fair value of all open positions, before considering the clearing houses’ ability to access defaulting clearing firms’ collateral deposits.
For cleared credit default swap and interest rate swap contracts, the maximum exposure related to CME’s guarantee would be one full day of changes in fair value of all open positions, before considering CME’s ability to access defaulting clearing firms’ collateral.
During 2017, the clearing house transferred an average of approximately $2.4 billion a day through the clearing system for settlement from clearing firms whose positions had lost value to clearing firms whose positions had gained value.
The clearing house reduces the guarantee exposure through initial and maintenance performance bond requirements and mandatory guaranty fund contributions.
The company believes that the guarantee liability is immaterial and therefore has not recorded any liability at December 31, 2017.
At December 31, 2016, performance bond and guaranty fund contribution assets on the consolidated balance sheets included cash as well as U. S.  Treasury and U. S.  government agency securities with maturity dates of 90 days or less.
The U. S.  Treasury and U. S.  government agency securities were purchased by CME, at its discretion, using cash collateral.
The benefits, including interest earned, and risks of ownership accrue to CME.
Interest earned is included in investment income on the consolidated statements of income.
There were no U. S.  Treasury and U. S.  government agency securities held at December 31, 2017.
The amortized cost and fair value of these securities at December 31, 2016 were as follows:
## Table 0 ##
CME has been designated as a systemically important financial market utility by the Financial Stability Oversight Council and maintains a cash account at the Federal Reserve Bank of Chicago.
At December 31, 2017 and December 31, 2016, CME maintained $34.2 billion and $6.2 billion, respectively, within the cash account at the Federal Reserve Bank of Chicago.
Clearing firms, at their option, may instruct CME to deposit the cash held by CME into one of the IEF programs.
The total principal in the IEF programs was $1.1 billion at December 31, 2017 and $6.8 billion at December 31, 2016.
CONTRACTUAL OBLIGATIONS AND COMMERCIAL COMMITMENTS A summary of our obligations to make future payments as of April 30, 2005 is as follows:
## Table 1 ##
In October 2004.  we issued $400.0 million of 5.125% Senior Notes, due 2014.
The Senior Notes are not redeemable by the bondholders prior to maturity.
The net proceeds of this transaction were used to repay the $250.0 million in 674% Senior Notes, which were due November 1， 2004.
The remaining proceeds were used for working capital, capital expenditures repayment of other debt and other general corporate purposes In April 2000， we issued $500.0 million of 8 2%6 Senior Notes due 2007.
The Senior Notes are not redeemable prior to maturity.
The net proceeds of this transaction were used to repay a portion of the short-term borrowings that initially funded the acquisition of OLDE.
Future payments related to Business Services acquisitions and apital lease obligations are included in long-term debt on our consolidated balance sheets.
Our debt to total capital ratio was 32.4% at April 30， 2005， compared with 31.1% at April 30， 2004 As of April 30， 2005 we had $850 million remaining under our shelf registration statement for additional debt issuances.
As a result of our failure to file this Form 10-K by the SECs prescribed due date, we may be unable to issue any debt securities under the shelf registration statement for a period of twelve months.
we intend to seek an adjustment of the filing date for this Form 10-K as permitted under SEC rules.
If such request is granted, we would regain the ability to issue debt securities under our shelf registration statement, although at this time the Company has no intention of doing so.
In connection with our acquisition of the non-attest assets of M&P in August 1999， we assumed certain pension liabilities related to M&Ps retired partners.
We make payments in varying amounts on a monthly basis.
which are included in other noncurrent liabilities Operating leases, although requiring future cash payments, are not included in our consolidated balance sheets A summary of our commitments as of April 30, 2005, which may or may not require future payments, expire as follows:
## Table 2 ##
See discussion of commitments in Item 8, note 17 to our consolidated financial statements.
NOTE 9: D ERIVATIVE INSTRUMENTS A summary of our derivative instruments as of April 30, 2005 is as follows:
## Table 3 ##
We use interest rate swaps and forward loan sale commitments to reduce interest rate risk associated with non-prime loans.
We generally enter into interest rate swap arrangements related to existing loan applications with ratelock commitments and, beginning at the end of our second quarter, for rate-lock commitments we expect to make in the next 30 days.
Interest rate swaps represent an agreement to exchange interest rate payments, effectively converting our fixed financing costs into a floating rate.
These contracts increase in value as rates rise and decrease in value as rates fall.
We enter into interest rate caps to mitigate interest rate risk associated with mortgage loans that will be securitized and residual interests that are classified as trading securities because they will be sold in a subsequent NIM transaction.
The caps enhance the marketability of the securitization and NM transactions.
An interest rate cap represents a right to receive cash if interest rates rise above a contractual strike rate, its value therefore increases as interest rates rise.
The interest rate used in our interest rate caps is based on LIBOR.
We enter into forward loan commitments to sell our non-prime mortgage loans to manage interest rate risk.
Forward loan sale commitments for non-prime loans are not considered derivative instruments and are therefore not recorded in our financial .
statements.
The notional value and the contract value of the forward commitments at April 30, 2005 were $8.7 billion and $8.9 billion, respectively.
Most of our forward commitments give us the option to under- or over-deliver by five to ten percent.
We, in the normal course of business, enter into commitments with our customers to fund both non-prime and prime mortgage loans for specified periods of time at "locked-in" interest rates.
These derivative instruments represent commitments to fund loans ("rate-lock equivalents").
The fair value of non-prime loan commitments is calculated using a binomial option model.
We adopted SEC Staff Accounting Bulletin No.105, “Application of Accounting Principles to Loan Commitments," as of March 31, 2004.
Upon adoption, we no longer record an asset for non-prime commitments to fund loans.
The fair value of prime loan commitments is calculated based on the current market pricing of short sales of FNMA, FHLMC and GNMA mortgage-backed securities and the coupon rates of the eligible loans.
We sell short FNMA, FHLMC and GNMA mortgage-backed securities to reduce our risk related to our commitments to fund fixed-rate prime loans.
The position on certain or all of the fixed- rate mortgage loans is closed approximately 10-15 days prior to standard Public Securities Association ("PSA") settlement dates.
We entered into an agreement with Household (subsequently acquired by HSBC) during fiscal year 2003, whereby we waived our right to purchase any participation interests in and receive license fees relating to RALs during the period January 1 through April 30, 2003.
In consideration for waiving these rights, we received a series of payments from Household, subject to certain adjustments based on delinquency rates on RALS made by Household through December 31， 2003.
This adjustment provision was accounted for as a derivative and was marked-to- market monthly through December 31, 2003.
Accordingly, during fiscal year 2004, we recognized $6.5 million of revenues related to this instrument.
The final settlement in accordance with this agreement was received in January 2004.
None of our derivative instruments qualify for hedge accounting treatment as of April 30, 2005 and 2004.
GAINS ON SALES OF MORTGAGE ASSETS>>> We sell substantially all of the non-prime mortgage loans we originate to the Trusts, which are qualifying special purpose entities ("QSPEs")，with servicing rights generally retained.
Prime mortgage loans are sold in whole loan sales, servicing released, to third-party buyers.
Gains on sales of mortgage assets are recognized when control of the assets is surrendered ( when loans are sold to Trusts) and are based on the difference between cash proceeds and the allocated cost of the assets sold.
We determine the allocated cost of assets sold based on the relative fair values of cash proceeds, MSRs and the beneficial interest in Trusts, which represents the ultimate expected outcome from the Trusts' disposition of the loans.
The relative fair value of the MSRs and the beneficial interest in Trust is determined using discounted cash flow models, which require various management assumptions, limited by the ultimate expected outcome from the disposition of the loans by the Trusts (see discussion below in“Valuation of Residual Interests" and “Valuation of Mortgage Servicing Rights").
The following is an example of a hypothetical gain on sale calculation:

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td>2016</td></tr><tr><td>(in millions)</td><td>AmortizedCost</td><td>FairValue</td></tr><tr><td>U.S. Treasury securities</td><td>$5,548.9</td><td>$5,549.0</td></tr><tr><td>U.S. government agency securities</td><td>1,228.3</td><td>1,228.3</td></tr></table>
<table><tr><td></td><td colspan="5">(in 000s)</td></tr><tr><td colspan="2"></td><td>Less Than</td><td colspan="2"></td><td>After</td></tr><tr><td></td><td>Total</td><td>1 Year</td><td>1 – 3 Years</td><td>4 – 5 Years</td><td>5 Years</td></tr><tr><td>Debt</td><td>$897,046</td><td>$45</td><td>$498,916</td><td>$91</td><td>$397,994</td></tr><tr><td>Long-term obligation to government</td><td>213,360</td><td>106,680</td><td>106,680</td><td>–</td><td>–</td></tr><tr><td>Acquisition payments</td><td>38,022</td><td>25,159</td><td>12,863</td><td>–</td><td>–</td></tr><tr><td>Pension obligation assumed</td><td>15,929</td><td>2,625</td><td>4,545</td><td>3,698</td><td>5,061</td></tr><tr><td>Capital lease obligation</td><td>13,550</td><td>341</td><td>730</td><td>997</td><td>11,482</td></tr><tr><td>Operating leases</td><td>708,611</td><td>229,768</td><td>313,264</td><td>124,945</td><td>40,634</td></tr><tr><td>Total contractual cash obligations</td><td>$1,886,518</td><td>$364,618</td><td>$936,998</td><td>$129,731</td><td>$455,171</td></tr></table>
<table><tr><td></td><td>Total</td><td>Less Than 1 Year</td><td>1 - 3 Years</td><td>4 - 5 Years</td><td>After 5 Years</td></tr><tr><td>Commitments to fund mortgage loans</td><td>$3,931,926</td><td>$3,931,926</td><td>$–</td><td>$–</td><td>$–</td></tr><tr><td>Commitments to sell mortgage loans</td><td>8,707,000</td><td>8,707,000</td><td>–</td><td>–</td><td>–</td></tr><tr><td>Pledged securities</td><td>44,609</td><td>44,609</td><td>–</td><td>–</td><td>–</td></tr><tr><td>Commitment to fund M&P</td><td>75,000</td><td>75,000</td><td>–</td><td>–</td><td>–</td></tr><tr><td>Franchise Equity Lines of Credit</td><td>68,949</td><td>20,122</td><td>20,476</td><td>28,351</td><td>–</td></tr><tr><td>Mortgage loan repurchase obligations</td><td>41,233</td><td>41,233</td><td>–</td><td>–</td><td>–</td></tr><tr><td>Construction of new building</td><td>143,116</td><td>103,505</td><td>39,611</td><td>–</td><td>–</td></tr><tr><td>Other commercial commitments</td><td>8,219</td><td>5,221</td><td>2,500</td><td>458</td><td>40</td></tr><tr><td>Total commercial commitments</td><td>$13,020,052</td><td>$12,928,616</td><td>$62,587</td><td>$28,809</td><td>$40</td></tr></table>
<table><tr><td></td><td colspan="5">(in 000s)</td></tr><tr><td></td><td colspan="2">Asset (Liability) Balance at April 30,</td><td colspan="3">Gain (Loss) in the Year Ended April 30,</td></tr><tr><td></td><td>2005</td><td>2004</td><td>2005</td><td>2004</td><td>2003</td></tr><tr><td>Interest rate swaps</td><td>$-1,325</td><td>$–</td><td>$47,192</td><td>$-2,703</td><td>$-5,194</td></tr><tr><td>Interest rate caps</td><td>12,458</td><td>–</td><td>-106</td><td>–</td><td>–</td></tr><tr><td>Rate-lock equivalents</td><td>801</td><td>-1,386</td><td>2,187</td><td>-13,917</td><td>6,158</td></tr><tr><td>Prime short sales</td><td>-805</td><td>2,080</td><td>-2,420</td><td>4,663</td><td>-5,105</td></tr><tr><td></td><td>$11,129</td><td>$694</td><td>$46,853</td><td>$-11,957</td><td>$-4,141</td></tr></table>

Question: what was the average balance within the cash account at the federal reserve bank of chicago for december 31 , 2017 and december 31 , 2016 , in billions?
Answer: 20.2
Reasoning program: add(34.2,6.2), divide(#0,const_2)