Ron is planning for retirement and hopes to make withdraws of $$4,900$ at the end of each month for $14$ years once he's retired. He plans on retiring in $20$ years.

$($a$)$ Find the amount that Ron must have in his retirement account in $20$ years from now in order to achieve his financial retirement goal assuming that once he is retired he will earn $6\%$ compounded monthly. $5$

$($b$)$ If Ron plans to work for another $20$ years and also plans to make monthly deposits in a retirement account during that time, how much should Ron deposit in the account each month so that he can achieve his financial retirement goal assuming that he can earn $10\%$ compounded monthly. $