Suggested improvement: do not use a variable name of "cd", as that conflicts with the commonly-used MATLAB routine cd() . Get out of the habit now of using variable names that match common MATLAB routines, before you get stuck calling your variables "sum" and having a heck of a time debugging your program.
Other than the above: You need to be more specific about what you were hoping for from us, keeping in mind that since this is an assignment you are doing, we are likely to avoid giving you anything that might be considered an "answer" to the assignment.
