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: a student travels from his house to school at 12 km / hr and reaches school 2 hours late. the next day he travels 20 km / hr and reaches school 1 hour early. what is the distance between his house and the school ?
Options: a. 90, b. 100, c. 110, d. 120, e. 130
[A]: a


[Q]: Problem: a and b started a business in partnership investing rs. 20,000 and rs. 15,000 respectively. after 6 months, c joined them with rs. 20,000. whatwill be b ' s share in total profit of rs. 15,000 earned at the end of 2 years from the startingof the business ?
Options: a. s. 5,000, b. s. 4,500, c. s. 5,700, d. s. 6,500, e. s. 7,500
[A]: b


[Q]: Problem: a man can row upstream at 25 kmph and downstream at 45 kmph, and then find the speed of the man in still water ?
Options: a. 11, b. 77, c. 30, d. 88, e. 35
[A]:
e