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 furniture dealer purchased a desk for $ 150 and then set the selling price equal to the purchase price plus a markup that was 40 % of the selling price. if the dealer sold the desk at the selling price, what was the amount of the dealer ' s gross profit from the purchase and the sale of the desk ?
Options: a. $ 40, b. $ 60, c. $ 80, d. $ 90, e. $ 100
[A]: e


[Q]: Problem: a train covers a distance of 100 km in 1 hour. if its speed is decreased by 15 km / hr, the time taken by the car to cover the same distance will be ?
Options: a. 1 hr, b. 1 hr 10 min, c. 50 min, d. 1 hr 30 min, e. 1 hr 45 min
[A]: b


[Q]: Problem: the speed at which a man can row a boat in still water is 150 kmph. if he rows downstream, where the speed of current is 48 kmph, what time will he take to cover 390 metres ?
Options: a. 10, b. 11, c. 12, d. 13, e. 14
[A]:
d