Hello sarahmrkhan, are you able to help me with this in 4 hours?

The total amount of interest expense over the bonds life is the same under both methods (straight line and effective interest). However, when the annual amounts are materially different, generally accepted accounting principles require use of the effective-interest method (Kieso et al, p.771). To give a better picture about rates, my question is what are the differences between a fixed rate mortgage and a variable rate mortgage? How could they impact the debt?