Subject: mathqa
Question: 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 10 % . their gross income from sales for one month decreases by what percent ?
Option: 
A: 1 %
B: 9 %
C: 5 %
D: 7 %
Answer: A