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 30%. Their gross income from sales for one month increases by what percent?	Choose the correct choice
A) 9 %	B) 11 %	C) 13 %	D) 15 %	E) 17 %

Rationale: let p be the original price and let x be the number of items sold originally . the original income is p * x . after the changes , the income is 0.9 p * 1.3 x = 1.17 * ( p * x ) , an increase of 17 % . the answer is e .
Answer: E