A software company sells three packages, Package A, Package B, and Package C, which retail for $99, $199, and $299, respectively. Quantity discounts are given according to the following table:
Quantity Discount
10 through 19 .....................20%
20 through 49..................... 30%
50 through 99 .....................40%
100 or more ........................50%
Create an application that allows the user to enter the number of units sold for each software package. The application's form should resemble Figure 4-37.
The application should calculate and display the order amounts and the grand total in a Label control. The Clear button must clear all text boxes and calculated labels. The Exit button must close the window.
Input validation: Make sure the number of units for each package is numeric, and is not negative.