Answer:
The total amount Arnold pay in interest is $ 2521.30
Step-by-step explanation:
Given :Arnold borrowed $7890 at 11.5 percent for five years.
We have to find the amount Arnold pay in interest
Using formula for monthly payment ,

Given : Principal value = $7890
Rate of interest = 11.5% anually
So monthly interest rate is 
Time = 5 years
In months 5 years = 5 × 12 = 60 month
Substitute, above we have,

Simplify, we get,
Monthly payment = $ 173.52
Total payment that Arnold pay = No. of months × Monthly Payment
⇒ Total Payment = 60 × 173.52
⇒ Total Payment = $ 10411.30
Since, Money Arnold borrowed = $7890
Thus, Amount of interest = Total payment - Amount borrowed
⇒ Interest = 10411.30 - 7890
⇒ Interest = $2521.30
Thus, The total amount Arnold pay in interest is $ 2521.30