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: of the diplomats who attended a summit conference: 20 spoke japanese, 32 did not speak russian and 20 % of the diplomats spoke neither japanese nor russian. if 10 % of the diplomats spoke both japanese and russian, then how many diplomats attended the conference ?
Options: a. 70, b. 96, c. 108, d. 120, e. 150

A: d
****
Q: Problem: the mean proportional between 4 and 16 is ?
Options: a. 12, b. 13, c. 14, d. 15, e. 16

A: e
****
Q: Problem: marketing executives for a certain chewing gum company projected a 40 percent increase in revenue this year over that of last year, but revenue this year actually decreased by 30 %. what percent of the projected revenue was the actual revenue ?
Options: a. 50 %, b. 58 %, c. 62.5 %, d. 64 %, e. 75 %

A:
a
****