you is $5\mathrm{.}25$ percent. You will make a down payment of $10$ percent of the purchase price.

a$.$ Calculate your monthly payments on this mortgage.

b$.$ Calculate the amount of interest and, separately, principal paid in the $20$ th payment.

c$.$ Calculate the amount of interest and, separately, principal paid in the $140$th payment.

d$.$ Calculate the amount of interest paid over the life of this mortgage.