On selling 20 balls at Rs. 720, there is a loss equal to the cost price of 5 balls. The cost price of a ball is:	Choose the correct option.
A) s . 48  B) s . 50  C) s . 55  D) s . 60  E) s . 70

Rationale: "( c . p . of 20 balls ) - ( s . p . of 20 balls ) = ( c . p . of 5 balls ) c . p . of 15 balls = s . p . of 20 balls = rs . 720 . c . p . of 1 ball = rs . 720 / 15 = rs . 48 . answer : option a"
Answer: A