This week you'll complete your project. Before you get started, check through for any corrections you need to make. Perhaps your instructor left comments from previous weeks that you want to incorporate. At this point, you should have a working copy of the program that displays practice programs for addition, subtraction, multiplication, and division. This week you will add secure code that will ensure accurate buffer flow and valid data. So now let's add the code for the remaining functionality. First, we will use the scanf_s() function to store the calculation letters (A, 'S, 'M; D) the user enters. You should also use the toupper() function from the ctype.h header file to ensure valid data is entered. This code might look as follows: scanf_s(" %c", &option, 1); option=toupper (option) ; Next, you will create a while() loop to check that the user has entered the calculation letters ('A', 'S', 'M'. 'D'), accepting these letters only as valid entries. Keep in mind that you will also need to use this while() loop inside of the loop of correct entries to check for data validity when the user continues to use the program