; and (2) may not be deferred or otherwise withheld from obligation during the 90-day period before the expiration of the period of availability of such budget authority, including, if applicable, the 90-day period before the expiration of an initial period of availability for which such budget authority was provided. (b) With respect to an apportionment of an appropriation made pursuant to section 1513(b) of title 31, United States Code, an appropriation (as that term is defined in section 1511 of title 31, United States Code) shall be apportioned— (1) to make available all amounts for obligation in sufficient time to be prudently obligated