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: subtracting 3 % of a from a is equivalent to multiplying a by how much ?
Options: a. 0.97, b. 9.4, c. 0.094, d. 94, e. none

Ex Output:
a


Ex Input:
Problem: a merchant sells an item at a 20 % discount, but still makes a gross profit of 20 percent of the cost. what percent of the cost would the gross profit on the item have been if it had been sold without the discount ?
Options: a. 20 %, b. 40 %, c. 50 %, d. 60 %, e. 75 %

Ex Output:
c


Ex Input:
Problem: surface area of a sphere is 2464 cm 2. if its radius is doubled, then the surface area of the new sphere will be
Options: ['a. 4920 cm 2', 'b. 4727 cm 2', 'c. 9856 cm 2', 'd. 19712 cm 2', 'e. none']

Ex Output:

c