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: a cement mixture is composed of 3 elements. by weight, 1 / 2 of the mixture is sand, 1 / 5 of the mixture is water, and the remaining 15 pounds of the mixture is gravel. what is the weight of the entire mixture in pounds ?
Options: a. 30, b. 40, c. 50, d. 60, e. 80

A: c
****
Q: Problem: the least number which when divided by 5, 6, 7 and 8 leaves a remainder 3, but when divided by 9 leaves no remainder, is :
Options: a. 2377, b. 1683, c. 2677, d. 9972, e. 1611

A: b
****
Q: Problem: two integers are in the ratio of 1 to 4. if 6 is added to the smaller number, the ratio becomes 1 to 3. find the larger integer.
Options: a. 4, b. 24, c. 30, d. 72, e. 80

A:
d
****