Detailed Instructions: 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:Problem: john and david can finish a job together in 4 hours. if john can do the job by himself in 5 hours, what percent of the job does david do ?
Options: a. 20 %, b. 25 %, c. 24 %, d. 23 %, e. 22 %
Solution:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
a