Car Dealership X, the total profit from sales increased by 30 percent over the previous years, while the number of cars sold decreased by 30 percent over the previous years. Approximately what was the average percent increase in profit per car over the previous year.
Choose the correct choice from the following choices:  A) 18 %  B) 30 %  C) 52 %  D) 63 %  E) 85.71 %

Rationale: let profit be x and cars sold be y originally profit / car = x / y now it is 1.3 x / 0.7 y = 13 / 7 ( x / y ) increase in profit per car = ( ( 6 / 7 ) ( x / y ) ) / ( x / y ) * 100 = 85.71 % answer = e
Answer: E