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 Input:
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 %

Ex Output:
e


Ex Input:
Problem: a mixture of 70 litres of milk and water contains 10 % water. how many litres of water should be added to the mixture so that the mixture contains 12 1 / 2 % water ?
Options: a. 2, b. 8, c. 6, d. 3, e. 4

Ex Output:
a


Ex Input:
Problem: if the ratio of the sum of the first 6 terms of a g. p. to the sum of the first 3 terms of the g. p. is 343, what is the common ratio of the g. p ?
Options: a. 3, b. 1 / 3, c. 2, d. 7, e. 1 / 7

Ex Output:

d