So I am actually confused with how to do loan mortgage problems in my textbook. I was wondering if someone can give me some insights to solving this problem:
Problem: Ten years ago the Peter's bought a house, taking out a 30 year mortgage for $130,000 at 4.5%. This year (exactly 10 years later) they refinanced the house, taking out a new 30 year mortgage for the remaining balance at 3.125%.
i) What was the monthly payment on the original 4.5% mortgage?
My thoughts for i) I am thinking we have to use the present value formula which is:
$$PV=R\times\frac{1-(1+i)^{-n}}{i}$$
So is PV here $130000?$ Is $i = 0.065?$? Can we take $n = 30?$ I have checked with my classmates and most of them seemed to have used Excel, but I was wondering how we can calculate this without Excel.
ii) What was the remaining balance after 10 years (the amount they then refinanced)?
iii) How much interest did they pay during those first 10 years?
iv) What is the monthly payment on the refinance 3.125% mortgage?
v) How much interest will they pay over the 30 year term of the refinance?
vi) How much total interest will they pay over the full 40 years the Peter's have a loan for the house?