4. Calculating Interest Rates. Solve for the unknown interest rate in each of the following: Years Interest Rate Future Value Present Value $ 221 425 25,000 40,200 4 8 16 25 $ 307 761 136,771 255,810 5. Calculating the Number of Periods. Solve for the unknown number of years in each of the following: Years Present Value Interest Rate Future Value $ 250 1,941 21,320 32,500 4% 9 23 34 $ 1,105 3,860 387,120 198,212