Bill and Joe each put 20 into separate accounts at time t = 0, where t is measured in years. Bill's account earns interest at a constant annual effective interest rate of K/36, K>0. Joe's account earns interest at a force of interest, 1/(K + 0.2t). At the end of five years, the amount in each account is X. Calculate X. 43.2 54.0 58.5 61.0 76.3