spreads

FYI.
I also had the same doubts, so I did the following calculation in excel using PMT functions. Hope it helps

number of years N annual interest rate I/Y FV PV type PMT
10 120 8% 0.00667 1 -1 0 $0.00667 $0.0800 annual interest rate
10 120 8% 0.00667 -1 0 0 $0.00547 $0.0656 sinking fund factor
10 120 8% 0.00667 0 -1 0 $0.01213 $0.1456 annual mortgage cost

for a better visibility, you could save the following as a csv file and open it in excel:
number of years,N,annual interest rate,I/Y,FV,PV,type,PMT,,
10,120,8%,0.00667,1,-1,0,$0.00667 ,$0.0800 ,annual interest rate
10,120,8%,0.00667,-1,0,0,$0.00547 ,$0.0656 ,sinking fund factor
10,120,8%,0.00667,0,-1,0,$0.01213 ,$0.1456 ,annual mortgage cost