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: if 8 gallons of gasoline are added to a tank that is already filled to 3 / 4 of its capacity, the tank is then filled to 9 / 10 of its capacity. how many gallons does the tank hold ?
Options: a. 20, b. 24, c. 36, d. 48, e. 60
d