Simple MATLAB programming please!

EXERCISE 2 Recall that a geometric sum is a sum of the form a + ar + ara + ar3 +.... (a) Write a function file called geomsum1 which accepts the values of r, a and n (in that order) as input arguments and uses a for loop to return the sum of the first n terms of the geometric series. Test your function for r = 4/5, a = 4, n = 8. (b) Write a function file called geomsum2 which accepts the values of r, a and n (in that order) as input arguments and uses the built in command sum to find the sum of the first n terms of the geometric series. Test your function for r = 4/5, a = 4, n= 8. Hint: Start by defining the vector e = [O:n-1) and then evaluate the vector R = r.^e. It should be easy to figure out how to find the sum from there