(a) require that bills be submitted promptly to it by vendors for services and supplies furnished to it by them;

(b) arrange to pay the bills promptly;

(c) however, except as provided in subdivision (d) of this section, in no event shall more than 12 months elapse between the month in which any services or supplies are furnished to the social services district and the month of payment for those services or supplies;

(d) in cases where payment of an item has been deferred pending final determination of a legal or administrative proceeding involving the liability of the social services district therefore, payment shall be made by the end of the third month following the month of final determination.