In this exercise, you modify the Sales application from Exercise 14 in Chapter 3. Use Windows to copy the Sales Solution folder from the VB2017\Chap03 folder to the VB2017\Chap04 folder. Open the Sales Solution.sln file contained in the VB2017\Chap04\Sales Solution folder. Start the application and then click the Calculate button. The percentages display as NaN, which stands for Not a Number. The NaN message is a result of dividing a number by 0. Use a selection structure to display 0.0% rather than NaN as the percentages. Save the solution and then start and test the application. Now professionalize the interface by allowing the text boxes to accept only numbers, the period, and the Backspace key. Save the solution and then start and test the application.