Detailed Instructions: 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.
Q: Problem: working alone, printers x, y, and z can do a certain printing job, consisting of a large number of pages, in 12, 20, and 20 hours, respectively. what is the ratio of the time it takes printer x to do the job, working alone at its rate, to the time it takes printers y and z to do the job, working together at their individual rates ?
Options: a. 4 / 11, b. 1 / 2, c. 15 / 22, d. 10 / 1, e. 11 / 4
A:
d