Answer:
P is the principal amount, $8000.00.
r is the interest rate, 9% per year, or in decimal form, 9/100=0.09.
t is the time involved, 18....year(s) time periods.
So, t is 18....year time periods.
To find the simple interest, we multiply 8000 × 0.09 × 18 to get that:
The interest is: $12960.00
