I am trying to write a program that uses a four argument constructor. It is an inventory program that contains item number, item name, unit price, and units in stock. I created a class Product with get and set methods for each. There is also a method to calculate the extended price. The Inventory class must pass three sets of data through the constructor and display the results for each product on one line. Appropriate column headings must also be displayed. I am having trouble with the inventory class displaying the variables and column headings. I cannot use arrays. Can anyone help me?