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: find the sum of first 89 odd numbers
Options: a. 7921, b. 4800, c. 7900, d. 4980, e. 4960
[A]: a


[Q]: Problem: a and b invests rs. 2500 and rs. 4000 respectively in a business. if a doubles his capital after 6 months. in what ratio should a and b divide that year ' s profit ?
Options: a. 11: 5, b. 15: 16, c. 15: 2, d. 9: 9, e. 11: 1
[A]: b


[Q]: Problem: two numbers are in the ratio of 2: 3. if 20 be subtracted from each, they are in the ratio of 10: 17. find the numbers ?
Options: a. 70,105, b. 60,88, c. 80,120, d. 60,84, e. 60,81
[A]:
a