Write an m-file to perform each of the following operations. Follow file-name, function-name, and function-argument instructions exactly. Please read instructions carefully and include the test file. There should be 2 functions, 1 for the calculation, another for the testing.

(b) An m-file entitled expmatrix.m containing a function expmatrix (A,n) that accepts an integer argument n and a square matrix A, and then computes the sum I+A+2!1A2+3!1A3+n!1An where I is the identity matrix whose size is the same as A, and ! is the factorial. Use FOR loop. Your code should give the warning message when the argument n is not a natural number or A is not square. In addition, make another m-file named test_expmatrix.m to show an example of expmatrix.m. To find the size of a matrix/vector variable, you can use the built-in function "size" in Matlab