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: kathleen can paint a room in 4 hours, and anthony can paint an identical room in 5 hours. how many hours would it take kathleen and anthony to paint both rooms if they work together at their respective rates ?
Options: a. 8 / 15, b. 40 / 9, c. 15 / 8, d. 9 / 4, e. 15 / 4
[EX A]: b

[EX Q]: Problem: what is the value of n if the sum of the consecutive odd intergers y from 1 to n equals 169 ?
Options: a. 47, b. 25, c. 37, d. 33, e. 29
[EX A]: b

[EX Q]: Problem: if the simple interest on a sum of money for 2 years at 5 % per annum is rs. 52, what is the compound interest on the same sum at the rate and for the same time ?
Options: a. s. 53.30, b. s. 53.22, c. s. 51.219, d. s. 53.18, e. s. 51.10
[EX A]:
a