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: an optometrist charges $ 150 per pair for soft contact lenses and $ 85 per pair for hard contact lenses. last week she sold 5 more pairs of soft lenses than hard lenses. if her total sales for pairs of contact lenses last week were $ 1,220, what was the total number of pairs of contact lenses that she sold ?
Options: a. 9, b. 13, c. 15, d. 17, e. 19

Ex Output:
a

Ex Input:
Problem: evaluate: 98612 / 22 * 11 * 70 = ?
Options: a. 700.4, b. 704.4, c. 740.4, d. 744.4, e. 700.0

Ex Output:
b

Ex Input:
Problem: if the price of sugar rises from rs. 10 per kg to rs. 11 per kg, a person, to have no increase in the expenditure on sugar, will have to reduce his consumption of sugar by
Options: a. 9 %, b. 20 %, c. 25 %, d. 30 %, e. none

Ex Output:
a