15 years x 12 months =180 months
$4,104 x 180 =$738,720 - total of principal + interest.
$738,720 - $505,500 =$233,220 - total amount of interest.
For Bria's mortgage, use this formula to calculate her monthly payment:
PMT=PV. R.{[1 + R]^N/ [1 + R]^N - 1}
PMT=179,000 x 0.032/12{[1+0.032/12]^(25*12) / [1 + 0.032/12]^(25*12) - 1}
PMT=477.33.... x 1.817546182......
PMT=$867.58 - Bria's monthly payment.