The payments are ...
A = P(r/n)/(1 -(1+r/n)^(-nt))
where P is the principal amount, $699,000*0.80 = $559,200
r is the annual interest rate, 0.05
n is the number of compoundings per year, 12
t is the number of years.
Then
A = 559,200*(0.05/12)/(1 -(1 +0.05/12)^(-12*35)) = 2822.21
The total of 420 of these payments is $1,185,328.20, which is $626,128.20 more than the loan amount.
Jamie's total finance charge is about $626,128.20.
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There is always some minor adustment required in the amount of the last payment. That has not been taken into account here.
