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.
--------
Question: Problem: the overall age of x and y is 19 year greater than the overall age of y and z. z is how many decades younger that x ?
Options: a. 11, b. 15, c. 12, d. 19, e. 20

Answer: d

Question: Problem: car x began traveling at an average speed of 35 miles per hour. after 72 minutes, car y began traveling at an average speed of 49 miles per hour. when both cars had traveled the same distance, both cars stopped. how many miles did car x travel from the time car y began traveling until both cars stopped ?
Options: a. 105, b. 120, c. 140, d. 147, e. 168

Answer: a

Question: Problem: one pipe can fill a tank four times as fast as another pipe. if together the two pipes can fill the tank in 36 minutes, then the slower pipe alone will be able to fill the tank in :
Options: a. 180 min, b. 144 min., c. 126 min, d. 114 min, e. 124 min

Answer:
a