Tom is a mushroom farmer. He invests all his spare cash in additional mush-rooms, which grow on otherwise useless land behind his barn. The mushrooms double in size during their first year, after which time they are harvested and sold at a constant price per pound. Tom’s friend Dick asks Tom for a loan of $ 200, which he promises to repay after 1 year. How much interest will Dick have to pay Tom in order for Tom to be no worse off than if he had not made the loan?