I know how to do part a. I need help solving for b using algebra.

a. You are planning to make monthly deposits of $400 into a retirement account that pays 10 percent interest compounded monthly. If your first deposit will be made one month from now, how large will your retirement account be in 30 years?

b. Instead of making monthly deposits, you are planning to make annual deposits of $4,800. How large will your account balance be in 30 years?