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 price of a book is increased from $ 300 to $ 390. what is the % of increase in its price ?
Options: a. 10 %, b. 20 %, c. 30 %, d. 35 %, e. 45 %

Answer: c


Question: Problem: a can do a job in 15 days and b in 20 days. if they work on it together for 4 days, then the fraction of the work that is left is ?
Options: a. 2 / 15, b. 8 / 15, c. 3 / 11, d. 1 / 12, e. 6 / 13

Answer: b


Question: Problem: 24 lbs of coffee p and 25 lbs of coffee v are mixed to make coffee x and y. the ratio of p to v in coffee x is 4 to 1, in y is 1 to 5. how much of p is contained in the mixture x ?
Options: a. 10, b. 20, c. 30, d. 40, e. 50

Answer:
b