Forecasting profit as a result of increasing energy costs

Question

Question: Forecasting profit as a result of increasing energy costs, the growth rate of the profit of the 4-yr old venice glassblowing company has begun to decline. Venice's management, after consulting with energy experts, decides to implement certain energy-conservation measures aimed at cutting energy bills. The general manager reports that, according to his calculations, the growth rate of venice's profit should be on the increase again within 4 yr. If venice's profit (in hundreds of dollars) t yr from now is given by the function

P(t) = t³ - 9t² + 40t + 50            (0 ≤ t ≤ 8)

Determine whether the general manager's forecast will be accurate.