In this task, you need to answer the given multiple-choice question on the gain. Gain is the value by which to multiply the input. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Input: Consider Input: Problem: the cost price of an article is 70 % of the marked price . calculate the gain percent after allowing a discount of 10 % . 
Options: a ) 13.6 % , b ) 28.6 % , c ) 35.6 % , d ) 42.3 % , e ) none

Output: b


Input: Consider Input: Problem: the difference between the compound interest compounded annually and simple interest for 2 years at 20 % per annum is rs . 72 . find the principal ? 
Options: a ) 2277 , b ) 2667 , c ) 3600 , d ) 2766 , e ) 1800

Output: e


Input: Consider Input: Problem: the population of a town is 7800 . it decreases annually at the rate of 10 % p . a . what was its population 2 years ago ? 
Options: a ) 9600 , b ) 8000 , c ) 8500 , d ) 9500 , e ) 10000


Output: a