A sailboat costs $$21,387.$ You pay $15\%$ down and amortize the rest with equal monthly payments over a $11-$year period. If you must pay $7\mathrm{.}2\%$ compounded monthly, what is your monthly payment? How much interest will you pay?

Monthly payments: $ $($Round to two decimal places.$)$

Interest: $ $($Round to two decimal places.$)$