The managers at Shoppers Haven wants an application that allows a store clerk to enter the item's original price and its discount rate. The discount rate ranges from 10% through 30% in increments of 5%. The default being 10%. The application should calculate and display the amount of the discount and also the discounted price. The code will read in the original price from the textbox and convert it to a double. The items in the listbox will be defaulted as a listbox object. Use the ToString() method to convert the object of the selected index to a string. From there, the rate can be converted to a double