(11 U.S.C. Sec. 1222(a)(2)(A) applies to taxes generated by post-petition sale of farm assets; debtor's calf inventory constituted a "farm asset" used in the debtor's farming operation for purposes of 11 U.S.C. Sec. 1222(a)(2)(A); debtor's "marginal method" of computing the amount of tax to be treated as a non-priority claim under 11 U.S.C. Sec. 122(a)(2)(A) is correct).