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 12%. Their gross income from sales for one month increases by what percent?  Choose the correct choice from the following options.
A) 0.4 %  B) 0.8 %  C) 2 %  D) 4 %  E) 8 %

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 * 1.12 x = 1.008 * ( p * x ) , an increase of 0.8 % . the answer is b ."
Answer: B