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 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
[EX A]: b

[EX Q]: Problem: if s is the sum of reciprocals of a list of consecutive integers from 55 to 64, inclusive, s is approximately equal to
Options: a. 0.16, b. 0.2, c. 0.3, d. 0.4, e. 0.5
[EX A]: a

[EX Q]: Problem: a boat can travel with a speed of 22 km / hr in still water. if the speed of the stream is 5 km / hr, find the time taken by the boat to go 135 km downstream
Options: a. 5 hours, b. 4 hours, c. 3 hours, d. 2 hours, e. none of these
[EX A]:
a