instruction:
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 present worth of rs. 2310 due years hence, the rate of interest being 15 % per annum, is :
Options: a. rs. 1440, b. rs. 1750, c. rs. 1680, d. rs. 1840, e. none of these
answer:
c

question:
Problem: if the ratio of two number is 6: 7 and lcm of the number is 450 then what is the number.
Options: a. 11, b. 20, c. 25, d. 30, e. 35
answer:
a

question:
Problem: find a two digit number, given that the sum of the digits is 9 and the difference of the digits is 3. ?
Options: a. 75, b. 63, c. 83, d. 94, e. 39
answer:
b