The factorial n! of a positive number (integer) is defined by: n! = n(n-1)(n-2)...3*2*1, where 0! = 1. Write a user difned fuction that calculates the factorial n! of a number. For the function name and arguments use y = fact(x), where the input argument y is the value x!. The function display an error message if a negative or a non-integer number is entered when the function is call.