Answer
The point, where the function decreases most rapidly is at t=2.5.
The airline had the most rapid increase in revenue in the midpoint of 2007.
Work Step by Step
At t=0 $P(t) is increasing.
At t=0.5 P(t) is also increasing.
At t=1 P(t) is changing from increasing to decreasing, therefore we can say that it is not yet decreasing.
At t=2.5 P(t) is decreasing.
At t=3.5 P(t) stops decreasing, but is not yet increasing.
The point, where the function decreases most rapidly is at t=2.5.
The airline had the most rapid increase in revenue in the midpoint of 2007 (2.5 years after 2005).
