shell scripts please need helps!system porgramming

= = . Write a shell script that will take two numbers as input and calculate "Cr and print the output. (i.e. n=4, r=2, output = 4!/ 2! 2!= 6). Include comments and handle exceptions as required. Show the code and a sample output. (Note: ! symbol means factorial of a number) (5 Marks) nCr = n! / r! (n r)