The reimbursable amount is the amount, if any, by which the amount of costs, determined under paragraph (a)(1) of this section exceeds the amount of payments determined under paragraph (a)(2) of this section. Where more than one claim is filed the aggregate reimbursable amount is the amount by which the total amount of costs, determined under paragraph (a)(1) of this section exceed the amount of Federal payments (in the case of a mutual aid agreement-its term or if none is determinable, the Federal fiscal year) determined under paragraph (a)(2) of this section.
44 C.F.R. §151.12