please while solving leave a space between A and B

Sally put an amount in a mutual fund investment fifteen years ago. If the balance is currently $72,000, how much must she have started with if the investment earned an average of 8% interest compounded semiannually? Assume that you saved $641,000 in a retirement account. The money is deposited in an account that earns 5% interest compounded Weekly. You want to retire and begin making weekly withdrawals from the account such that the money (principal and interest) lasts exactly 23 years. What is the amount of the weekly withdrawal