Given the task definition and input, reply with output. 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: on june 1 a bicycle dealer noted that the number of bicycles in stock had decreased by 3 for each of the past 5 months. if the stock continues to decrease at the same rate for the rest of the year, how many fewer bicycles will be in stock on september 1 than were in stock on january 1 ?
Options: a. 8, b. 12, c. 24, d. 32, e. 36
c