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.

Problem: a train running at the speed of 20 km / hr crosses a post in 10 seconds. what is the length of the train ?
Options: a. 150, b. 250, c. 415, d. 200, e. 312
d

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
e

Problem: a worker is paid a regular rate of rs. 30 for completing a survey. the worker completes 100 surveys per week. for any survey involving the use of her cellphone, she is paid at a rate of that is 20 % higher than her regular rate. if she completed 50 surveys involving the use of her cellphone, how much did she get that week ?
Options: a. 2200, b. 1100, c. 2500, d. 2800, e. 3300

e