If the monthly payment is m, the monthly interest rate is r, the number of payment (months) is n, and the principal is P, we have

,

With the value of n=180, r=0.045/12=0.00375, m=820,

P=107190.48

So the total price is the down payment plus the principal, which is

24252+107190.48 = 13142.48

The total payment for the loan is 820 × 180 =147600,

So the total interest is 147600-107190.48=40409.52