Instructions: 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: Problem: a man sold 20 articles for $ 60 and gained 20 % . how many articles should he sell for $ 80 to incur a loss 20 % ? 
Options: a ) 45 , b ) 36 , c ) 40 , d ) 50 , e ) 48
Output:
c