You need a $30-$year, fixed$-$rate mortgage to buy a new home for $$250,000.$ Your mortgage bank will lend you the money at a $6\mathrm{.}6$ percent APR for this $360-$month loan. However, you can afford monthly payments of only $$900,$ so you offer to pay off any remaining loan balance at the end of the loan in the form of a single balloon payment.

How large will this balloon payment have to be for you to keep your monthly payments at $$900?$