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.

[EX Q]: Problem: a theater box office sold an average ( arithmetic mean ) of 63 tickets per staff member to a particular movie. among the daytime staff, the average number sold per member was 78, and among the evening staff, the average number sold was 60. if there are no other employees, what was the ratio of the number of daytime staff members to the number of evening staff members ?
Options: a. 2: 3, b. 1: 4, c. 1: 5, d. 6: 11, e. 4: 7
[EX A]: c

[EX Q]: Problem: if a man lost 10 % by selling oranges at the rate of 12 a rupee at how many a rupee must he sell them to gain 44 % ?
Options: a. 6.5, b. 7.5, c. 7, d. 8, e. 2
[EX A]: b

[EX Q]: Problem: if 8 workers can build 8 cars in 8 days, then how many days would it take 4 workers to build 4 cars ?
Options: a. 2, b. 4, c. 8, d. 12, e. 16
[EX A]:
c