You will be given a definition of a task first, then some input of the task.
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.

Problem: in a group of 90 students, 30 are taking history, and 32 are taking statistics. if 59 students are taking history or statistics or both, then how many students are taking history but not statistics ?
Options: a. 9, b. 19, c. 33, d. 27, e. 31
Output:
c