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: 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
[EX A]: c

[EX Q]: Problem: farm tax is levied on the 45 % of the cultivated land. the tax department collected total $ 3840 through the farm tax from the village of mr. willam. mr. willam paid only $ 480 as farm tax. the percentage of total land of mr. willam over the total taxable land of the village is :
Options: a. 15 %, b. 25 %, c. 15.125 %, d. 27.78 %, e. none
[EX A]: d

[EX Q]: Problem: the lcm of two numbers is 2310 and hcf is 30. if one of the numbers is 210. then what is the other number ?
Options: a. 715, b. 825, c. 330, d. 582, e. 465
[EX A]:
c