On increasing the price of T.V. sets by 30%, their sale decreases by 20%. What is the effect on the revenue receipts of the shop ?  Choose the correct choice from the following answers:
A) 4  B) 5  C) 56  D) 2  E) 7

Rationale: "explanation : let the price be = rs . 100 , and number of units sold = 100 then , sale value = rs . ( 100 × 100 ) = rs . 10000 new sale value = rs . ( 130 × 80 ) = rs . 10400 increase % = 4001000040010000 × 100 = 4 % answer : a"
Answer: A