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: a company wants to spend equal amounts of money for the purchase of two types of computer printers costing $ 400 and $ 350 per unit, respectively. what is the fewest number of computer printers that the company can purchase ?
Options: a. 11, b. 13, c. 15, d. 17, e. 19
c