You decide to open a retirement account at your local bank that pays $8(\%)/($y$)$ea$($r$)/($m$)$onth $(8\%$ per year compounded monthly$).$ For the next

$20$ years, you will deposit $$600$ per month into the account, with all deposits and withdrawals occurring at month's end. On the day of

the last deposit, you will retire. Your expenses during the first year of retirement will be covered by your company's retirement plan.

As such, your first withdrawal from your retirement account will occur on the day exactly $12$ months after the last deposit.

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a$)$What monthly withdrawal can you make if you want the account to last $25$ years?

b$)$What monthly withdrawal can you make if you want the account to last forever $($with infinite withdrawals$)?$