Problem
Create a Inventory class to be used in online shopping application. The class must keep inventory and prices for three types of products: shampoo, conditioner and gel. Prices are in reward points. Upon request it should display the number of products of each kind that can be purchased by a customer based on their points. Inventory class can receive requests to purchase different product types. Each purchase method receives customer's number of points and a desired product quantity. The method must return customer's remaining number of points after purchase. Upon every sale appropriate inventory must be updated and displayed as well as customer's purchase options. In the Main method prompt the user to enter the number of points and then display the inventory and user's purchase options. Main method should make a purchase of each kind of product.