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.

[EX Q]: Problem: of all the homes on gotham street, 1 / 3 are termite - ridden, and 4 / 7 of these are collapsing. what fraction of the homes are termite - ridden, but not collapsing ?
Options: a. 1 / 3, b. 1 / 4, c. 1 / 5, d. 1 / 6, e. 1 / 7
[EX A]: e

[EX Q]: Problem: if a sum of money doubles itself in 20 years at simple interest, the ratepercent per annum is
Options: a. 12, b. 12.5, c. 13, d. 5, e. 14
[EX A]: d

[EX Q]: Problem: the charge for a single room at hotel p is 20 percent less than the charge for a single room at hotel r and 10 percent less than the charge for a single room at hotel g. the charge for a single room at hotel r is what percent greater than the charge for a single room at hotel g ?
Options: a. 15 %, b. 20 %, c. 12.5 %, d. 50 %, e. 150 %
[EX A]:
c