Amount of lawnowner bought by Sarah=$320
Down payment by Sarah= $100
Sarah paid in 12 months = 12 x 25 $ = 300$
$ paid by sarah = 300+12$=400$
Excess amount paid as interest by sarah=400-320=80$
yearly rate of interest paid by sarah = 80/320 x 100=25%
so 25% yearly interest was paid by sarah, so the correct option is C. hope this helps.