Task: Question Answering
Input (English): Problem: a couple who own an appliance store discover that if they advertise a sales discount of 10 % on every item in the store , at the end of one month the number of total items sold increases 15 % . their gross income from sales for one month increases by what percent ? 
Options: a ) 1.5 % , b ) 2.5 % , c ) 3.5 % , d ) 4.5 % , e ) 5.5 %
Output (English): c