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: 10 ^ ( 600 ) ã · 10 ^ ( 580 ) = ?
Options: a. 10 ^ 10, b. 10 ^ 20, c. 10 ^ 22, d. 10 ^ 23, e. 10 ^ 24

Ex Output:
b


Ex Input:
Problem: bottle r contains 350 capsules and costs $ 6.25. bottle t contains 130 capsules and costs $ 2.99. what is the difference between the cost per capsule for bottle r and the cost per capsule for bottle t ?
Options: a. $ 0.25, b. $ 0.12, c. $ 0.0052, d. $ 0.003, e. $ 0.002

Ex Output:
c


Ex Input:
Problem: in a new housing development, trees are to be planted along the sidewalk of a certain street. each tree takes up one square foot of sidewalk space, and there are to be 12 feet between each tree. how many trees can be planted if the road is 157 feet long ?
Options: a. 8, b. 9, c. 10, d. 11, e. 13

Ex Output:

e