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'.

[EX Q]: Problem: a shopkeeper sold an article at $ 100 with 10 % profit . then find its cost price ?
Options: a ) $ 120 , b ) $ 100 , c ) $ 91 , d ) $ 72 , e ) $ 69
[EX A]: c

[EX Q]: Problem: a shopkeeper sells his goods at cost price but uses a faulty meter that weighs 800 grams . find the profit percent .
Options: a ) 20 , b ) 15 , c ) 25 , d ) 18 , e ) 19
[EX A]: c

[EX Q]: Problem: a store reduced the price of all items in the store by 10 % on the first day and by another 10 % on the second day . the price of items on the second day was what percent of the price before the first reduction took place ?
Options: a ) 80.0 , b ) 80.9 , c ) 81.0 , d ) 81.1 , e ) 81.9
[EX A]:
c