When the user enters their choice for the calculator operation (+, -,*, or /) it should be a number between 1 and 4 (or 0 and 3). In the original version of the program if the user entered an illegal value no operation was performed Modify the program so that anytime the user enters an illegal operation an error message is printed and the user is asked for a new value. This will require adding a loop whose condition is based on the user's choice. In the initial version of the program it would perform one operation and then exit. Change the program so that when it finishes a calculation it asks the user if they want to perform another calculation. You can have the user enter a 0 for no and 1 for yes, or look up the char variable type so they can enter n or y Add an additional calculation to the calculator. This calculation should sum all of the integers between the two numbers the user entered (truncating the numbers if the user entered a decimal). For example, if the user entered 5.2 and 8.7 then the calculator should sum all of the values between 5 and 8 (i.e. 5 + 6 + 7 + 8). Remember that if you store a double value in an int variable it is automatically truncated