A fishy story problem?

Question

"A 1991 report estimated that there were 692 salmon in the Green River. If the population is expontentially decreasing at the rate of e^0.09 per year, what is the expected population in 2009? Round your answer to the nearest integer. "

I want to know the answer and see if i did it right, since my test won't give me it afterwards

Answer 1

F= 692 *e-0.09 t
Supposing that 692 are at the beginning of 1991 ,At the beginning of 2009 there are
692*e^-0.09*18 =137 salmons