$8.$ Knowledge and Understanding: Natalie and Preston would like to accumulate $$25000$ at the end of $3\mathrm{.}5$ years for a future down payment on a house in Prescott. How much should they deposit at the end of each week in a savings pays $7\mathrm{.}2\%/$a$,$ compounded monthly, to meet their goal? $($a$)$ Draw a time line to represent the annuity. $($b$)$ Write the series that represents the amount of the annuity. $($c$)$ Determine the weekly deposit.