A lake initially contains 2000 fish. Suppose that in the absence of predators or other causes of removal, the fish population increases by 6% each month. However, factoring in all causes, 150 fish are lost each month.
a. Explain why the fish population after $n$ months is modeled by $P_{n}=1.06 P_{n-1}-150$ with $P_{0}=2000$ .
b. How many fish will be in the pond after one year?