Definition: 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.
Input: Problem: a survey was sent to 65 customers, 7 of whom responded. then the survey was redesigned and sent to another 63 customers, 9 of whom responded. by approximately what percent did the response rate increase from the original survey to the redesigned survey ?
Options: a. 2 %, b. 4 %, c. 14 %, d. 28 %, e. 63 %
Output:
b