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: 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
[EX A]: d

[EX Q]: Problem: given that p is a positive even integer with a positive units digit, if the units digit of p ^ 3 minus the units digit of p ^ 2 is equal to 0, what is the units digit of p + 4 ?
Options: a. 7, b. 8, c. 10, d. 11, e. 12
[EX A]: c

[EX Q]: Problem: 5 / 8 of 3 / 10 of a number is greater than 4 / 9 of 1 / 4 of the same number by 55. what is half of that number ?
Options: a. 310, b. 312, c. 320, d. 314, e. 360
[EX A]:
e