(a) Directly or indirectly, for himself or herself or as an agent or partner of others, borrow any of its funds or deposits or in any manner use the same except to make such current and necessary payments as are authorized by the comptroller, or

(b) Become an endorser, surety or an obligor in any manner of monies loaned by or borrowed of such funds. h. The police and fire retirement system may use a part of its funds, not exceeding ten per centum of its assets, (1) for purchasing or leasing of land in the city of Albany and the construction thereon of a suitable office building or buildings for the transaction of the business of the retirement system, (2) for purchasing or leasing of land in the cities of Albany, Syracuse, Buffalo, Binghamton, New York, Rochester and Utica and the construction thereon of a suitable office building or buildings for purposes of lease or sale to the state, (3) for purchasing or leasing of land in the city of Albany on the north and south sides of Washington avenue commonly known as the "Campus Site" acquired by the state for a state building site pursuant to the provisions of chapter five hundred seventy-two of the laws of nineteen hundred forty-seven and the construction thereon of power plants including service connections, electric substations including service connections, garages, warehouses and restaurant facilities deemed necessary for the efficient and economical operation of the office building or buildings constructed on such land and (4) for purchasing or leasing of land in the city of Albany acquired by the state for suitable parking facilities for the use primarily of employees of the state and persons having business with state departments and state agencies and the construction thereon of such structures, appurtenances and facilities deemed necessary for the efficient and economical operation of the parking facilities constructed on such land and (5) for purchasing or leasing of land in locations approved by the state university trustees and the construction, acquisition, reconstruction, rehabilitation or improvement of suitable buildings or facilities thereon for purposes of lease or sale to the state university construction fund, such buildings or facilities to be used by the state university or by state-operated institutions or statutory or contract colleges under the jurisdiction of the state university or by the students, faculty and staff of the state university or of any such state-operated institution or statutory or contract college, and their families. The police and fire retirement system from time to time may lease to any public agency any portion of a building constructed for the transaction of its business which may not be required for such purpose, upon such terms and conditions as shall be deemed to be for the best interest of the police and fire retirement system. Real property of the police and fire retirement system acquired or constructed pursuant to this subdivision shall be exempt from taxation. i. At the close of each fiscal year, the average rate of investment earnings of the retirement system shall be computed by the actuary and certified to the comptroller. This rate shall be determined from the investment earnings during the calendar year which ended three months prior to the close of the fiscal year. For any year that such average rate of earnings is in excess of three per centum but not in excess of four per centum, the comptroller shall declare a rate of special interest, for members earning regular interest of three per centum, equal to the difference between such average rate of earnings and three per centum, expressed to the lower one-tenth of one per centum, but not in excess of one per centum. For any year, commencing with the fiscal year the first day of which is April first, nineteen hundred seventy, that such average rate of earnings is in excess of four per centum, the special rate of interest for members earning regular interest of three per centum shall be equal to the difference between such average rate of earnings and three per centum, expressed to the lower one-tenth of one per centum, but not in excess of two per centum, and for members earning regular interest of four per centum, it shall be the difference between such average rate of earnings and four per centum, expressed to the lower one-tenth of one per centum, but not in excess of one per centum. Special interest at such rates, shall be credited, by the comptroller at the same time that regular interest is credited, to the individual annuity savings accounts of persons who are members as of the close of the fiscal year. Special interest shall not be considered in determining rates of contribution of members. In the case of persons who last became members on or after July first, nineteen hundred seventy-three, the provisions of this subdivision shall apply only to the fiscal years beginning April first, nineteen hundred seventy-two and ending March thirty-first, nineteen hundred seventy-three. j. The retirement system may invest, within the limitations authorized for investments in conventional mortgages, a part of its funds in first mortgages on real property located anywhere within the boundaries of the United States and leased to the government of the United States, provided however, that no such investment shall be made unless the terms of the mortgage shall provide for amortization payments in an amount sufficient to completely amortize the loan within the period of the lease.