Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Problem: bob wants to run a mile in the same time as his sister. if bob ’ s time for a mile is currently 11 minutes 20 seconds and his sister ’ s time is currently 9 minutes 36 seconds, by what percent does bob need to improve his time in order run a mile in the same time as his sister ?
Options: a. 3 %, b. 5 %, c. 8 %, d. 10 %, e. 15 %
e

Problem: what is the probability of getting a queen or spade from a set of cards ?
Options: a. 3 / 13, b. 4 / 13, c. 5 / 13, d. 6 / 13, e. 7 / 13
b

Problem: there is 60 % increase in an amount in 6 years at simple interest. what will be the compound interest of $ 12,000 after 3 years at the same rate ?
Options: a. $ 2160, b. # 3120, c. $ 3972, d. $ 6240, e. none of these

c