To the closest year, how long will it take $200 to double if it is deposited and earns the following rates? [Notes: (1) See the hint for Problem 2-1. (2) This problem cannot be solved exactly with some financial calculators. For example, if you enter PV 
200, PMT  0, FV  400, and I  7 in an HP-12C, and then press the N key, you will get 11 years for part

a. The correct answer is 10.2448 years, which rounds to 10, but the calculator rounds up. However, the HP-

10B and HP-17B give the correct answer.]

a. 7 percent.

b. 10 percent.

c. 18 percent.

d. 100 percent.