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: if ( x - 10 ) ( y - 5 ) ( z - 2 ) = 1000 then what is the least value of x + y + z ? if x, y, z are all integer no.
Options: a. 7, b. 8, c. 9, d. 10, e. 11

Ex Output:
a

Ex Input:
Problem: find the smallest number that should be multiplied with 54000 to make it a perfect cube.
Options: ['a. 4', 'b. 5', 'c. 6', 'd. 3', 'e. 7']

Ex Output:
a

Ex Input:
Problem: if a person walks at 20 km / hr instead of 10 km / hr, he would have walked 40 km more. the actual distance traveled by him is ?
Options: a. 40 km, b. 76 km, c. 18 km, d. 16 km, e. 97 km

Ex Output:
a