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.

Example Input: Problem: bruce and anne can clean their house in 4 hours working together at their respective constant rates. if anne ’ s speed were doubled, they could clean their house in 3 hours working at their respective rates. how many w hours does it currently take anne to clean the house on her own ?
Options: a. 6, b. 7, c. 8, d. 12, e. 14
Example Output: d

Example Input: Problem: together, 15 type a machines and 7 type b machines can complete a certain job in 4 hours. together 8 type b machines and 15 type c machines can complete the same job in 11 hours. how many q hours would it take one type a machine, one type b machine, and one type c machine working together to complete the job ( assuming constant rates for each machine. ?
Options: a. 22 hours, b. 30 hours, c. 44 hours, d. 60 hours, e. it can not be determined from the information above.
Example Output: c

Example Input: Problem: a school has 4 section of chemistry in class x having 40, 35, 45 and 42 students. the mean marks obtained in chemistry test are 50, 60, 55 and 45 respectively for the 4 sections. determine the overall average of marks per student.
Options: a. 50.25, b. 52.25, c. 51.25, d. 53.25, e. none of the above
Example Output:
b