Derive a class BuyNItemsGetOneFree from DiscountPolicy, as described in Exercise 10. The class should have a constructor that has a single parameter n. In addition, the class should define the method computeDiscount so that every nth item is free. For example, the following table gives the discount for the purchase of various counts of an item that costs $10, when n is 3:

Exercise 10.

Create an abstract class DiscountPolicy. It should have a single abstract method computeDiscount that will return the discount for the purchase of a given number of a single item. The method has two parameters, count and itemCost.

count 1 2 3 4 6 7 Discount 10 10 20 20 10