correct, the system gives an error message "This input is invalid.". If the calculator works correctly, it prints out the following: >>> Calculator Give a number: hah, NEVER This input is invalid. Give a number: What? This input is invalid. Give a number: 100 Give a number: Just kidding This input is invalid. Give a number: 50 (1) + (2) - (3) (4) / (5) sin (number 1/ number 2 ) (6) cos (number 1/ number 2 ) (7) Change numbers (8)Quit Current numbers: 10050 Please select something (16):2 The result is: 50 (1) + (2) - (3) * (4) / (5) sin (number 1/ number 2 ) (6) cos (number 1/ number 2 ) (7) Change numbers (8)Quit Current numbers: 10050 Please select something (16):8 Thank you