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: if the average ( arithmetic mean ) of a and b is 45 and the average of b and c is 80, what is the value of c − a ?
Options: a. 25, b. 60, c. 90, d. 140, e. it can not be determined from the information given.
[EX A]: b

[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: 18 women can complete a work in 7 days and 10 children take 14 days to complete the work. how many days will 5 women and 10 children take to complete the work ?
Options: a. 8 days, b. 6 days, c. 7 days, d. 9 days, e. 1 days
[EX A]:
d