PUBLIC LAWS-- . 779-AUG. 7 , 1946 Optional deposits. Refunda Po, p. 880. Retirement and an- nuity fund. 41 Stat. 387, 388. D. 0. Code §j 31- 702, 31-707. separate accounts. Voluntary retire- ment. compounded annually from June 30 of the year in which the deduc- tions are made. These individual interest-bearing accounts shall be kept by the Auditor of the District of Columbia. Any teacher may at his option and under such regulations as may be prescribed by the Commissioners of the District of Columbia deposit with the Collector of Taxes, District of Columbia, additional sums in multiples of $25 but not to exceed 10 per centum per annum of his annual salary, pay, or compensation, for services rendered since March 1, 1920, which amount together with interest thereon at 3 per centum per annum compounded as of June 30 of each year, shall, at the date of his retirement, be available to purchase an annuity as he shall elect in accordance with such rules and regulations as may be prescribed by the Commissioners of the District of Columbia, in addition to the annuity provided by this Act; the purchase price of such annuity shall be based upon an interest rate of 3 per centum per annum compounded annually and upon such table of mortality as shall from time to time be prescribed by the Commissioners of the Dictrict of Columbia. In the event of death or separation from the service of such teacher before becoming eligible for retirement on annuity, the amounts so deposited with interest at 3 per centum com- pounded annually from June 30 of the year in which the deposits are made shall be refunded in accordance with the provisions of sec- tions 9 and 10, respectively, of this Act. A separate individual account shall be kept by the Auditor of the District of Columbia with respect to the voluntary deposits and interest of each teacher. Sr. 2 . The amounts so deducted and withheld from the annual salary of every teacher, and the amounts of additional voluntary deposits, shall be deposited in the Treasury of the United States to the credit of the teachers' retirement and annuity fund. As of the effective date of this Act, there shall be transferred and credited to such fund the balances of funds held for the retirement of teachers under the provisions of sections 2 and 7 of the Act of January 15, 1920, as amended. The fund thus created shall be held and invested by the Secretary of the Treasury until paid out as hereinafter pro- vided, and the income derived from such investment shall constitute a part of said fund for the purpose of carrying out the provisions of this Act. Separate accounts shall be maintained by the Treasury with respect to (1) the regular operations of the retirement system exclu- sive of those incident to the voluntary deposits; and (2) the voluntary deposits and the supplementary annuities and refunds resulting from such deposits. SEC. 3. (a) Any teacher to whom this Act applies who shall have attained or shall hereafter attain the age of sixty years and has ren- dered at least thirty years of service computed as prescribed in section 8 of this Act, or shall hereafter attain the age of sixty-two years and has rendered at least fifteen years of service computed as prescribed in section 8 of this Act, may voluntarily retire and shall be eligible for retirement on an annuity computed as provided in section 5 of this Act. (b) Any teacher to whom this Act applies who shall have attained or shall hereafter attain the age of fifty-five years and has rendered at least thirty years of service computed as prescribed in section 8 of this Act, may voluntarily retire and shall be paid an immediate life annuity beginning on the first day of the month following the date of separation from the service having a value equal to the present worth of a deferred annuity at the age of sixty years computed as prescribed in section 5 of this Act or may elect to receive a deferred annuity beginning at the age of sixty years computed as prescribed in section 5 of this Act. (c) Any teacher who shall have attained or shall hereafter attain 876 [60 STAT.