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: ramesh purchased a refrigerator for rs. 12500 after getting a discount of 20 % on the labelled price. he spent rs. 125 on transport and rs. 250 on installation. at what price should it be sold so that the profit earned would be 18 % if no discount was offered ?
Options: a. 17608, b. 17606, c. 17604, d. 17600, e. 18880
[EX A]: e

[EX Q]: Problem: a man goes downstream at 10 kmph, and upstream 8 kmph. the speed of the stream is
Options: a. 0 kmph, b. 4 kmph, c. 1 kmph, d. 2.5 kmph, e. 26 kmph
[EX A]: c

[EX Q]: Problem: p, q and r together earn rs. 1890 in 9 days. p and r can earn rs. 600 in 5 days. q and r in 7 days can earn rs. 910. how much amount does r can earn per day ?
Options: a. s. 40, b. s. 70, c. s. 90, d. s. 100, e. s. 120
[EX A]:
a