At first you need to know total cost (875)(1.05)=918.75According to the fact that you have already paid for 7 months, we have to subtract  700=218.75  what still needs to be payedOn the 8 moth you have missed the payment so  (218.75)(8/12), and remaining moths are  nearly 145.83333To finish, multiply by the apr and you will get $20.78 interest charged. So, I am pretty sure that he answer is D.