Exercise 1: compute the sum of two numbers supplied by the user, and display the result in a listbox:

Exercise 2: compute the sum and product of two numbers supplied by the user, and display the result in a listbox(Note: when you click button “Compute Product”, the product of the two numbers should be displayed in textbox “Product”, and nothing in “Sum:”, and vice versa, if you want to compute the sum, the result should be displayed in “Sum:”, but nothing in “Product” ):