Task: Question Answering
Input (English): Problem: a company decreased the price of its main product by 20 % . subsequently , the number of units sold increased such that the total revenue remained unchanged . what was the ratio of the percent increase in the units sold to the percent decrease of the original price for this product ? 
Options: a ) 3.0 , b ) 7.0 , c ) 5.0 , d ) 2.0 , e ) 1.0
Output (English): c