Melanie wants to deposit $550 at the end of each month into an investment account. At the end of 7 years he wants to stop depositing and start withdrawing an equal amount at the end of each month for the next 4 years. The investment earns 5.5% compounded monthly.

a. How much did Melanie have accumulated in seven years?

b. How much can Melanie withdraw at the end of each month for four years?