I'll just give you an answer based on my understanding.
I'll use the formula for compounding interest.
A = P(1+r/n)^nt
A = future value of the loan including interest
P = principal of the loan
r = interest rate
n = number of times the interest is compounded per year (monthly=12)
t = number of years the money is loaned for
Given:
P = 12,450
r = 7.3%, compounded monthly
t = 10 years
A = 12,450 (1+0.073/12)^12*10
A = 12,450 (1.006)¹²⁰
A = 12,450 (2.05)
A = 25,522.50
25,522.50 - 12,450 = 13,072.50 total interest paid.