As the error says, you can't directly execute an m-file which defines a function; you Call the function from a script or another function.
To call the function you would simply incorporate the line
final_project_mc(b)
at the end of the script which would return the output array at the command line as the default variable ans or assign it to a variable as
end_result = final_project_mc(b);
See
doc function % for more details
and section on programming for how scripts and functions work in the "Getting Started" section.
