Compute the face value of a $30-$year fixed$-$rate mortgage with a monthly payment of $$1,200,$ assuming a nominal interest rate of $6\%.$ Compute the face value if the interest rate is now $7\%.$ What is the difference in maximum house prices if both mortgages require $5\%$ down?

when i plug in the values in my financial calculator i get $200,149\mathrm{.}94$ for the $6\%$ and $180,369\mathrm{.}08$ for the $7\%,$ Why? Also, do i need to account for the $5\%$ down payment?