You have a mortgage of $125,600.00 at a 4.95% apr. you make a payment of $1,500.00 each month. what is your principal balance at the beginning of the third month? $122,600.00 $123,632.15 $123,636.20 $122,654.30 can someone me write it that out

Monthly Interest = Yearly Interest / 1200
Interest Paid = Previous Balance * Monthly Interest Rate
Equity = Monthly Payment -Interest Paid
New Balance = Previous Balance -Equity

Monthly Interest = 0.004125

After the FIRST payment
Interest Paid = 125,600.00 * .004125
Interest Paid = 518.10
Equity = 1,500.00 - 518.10
Equity =  981.90

New Balance = 125,600.00 -981.90
124,618.10

After the SECOND payment
Interest Paid = 124,618.10 * .004125
Interest Paid =  514.05
Equity = 1,500.00 - 514.05
Equity = 985.95

New Balance = 124,618.10 -985.95 =
123,632.15
Answer is B

I guess they want it for the BEGINNING of the third month and this is it.
I calculated it for the END of the third month so here it is.

After the THIRD payment
Interest Paid = 123,632.15 * .004125
Interest Paid = 509.98
Equity = 1,500.00 - 509.98
Equity = 990.02
New Balance = 123,632.15 -990.02 =
122,642.13

Source:
http://www.1728.org/loanmath.htm