Answer:
a) Alawys positive: t = 0 to a
b) Decreasing at an increasing rate: t = a to b
Step-by-step explanation: The population is increasing most rapidly during the period the curve in rising. The derivative of this line (i.e., the slope at any point t) will be positive until it t reaches a, the peak. The slope at this point is zero, and it sill be negative after that point. The values of t for which the slope is always positive are from 0 to a. The population is decreasing at an increasing rate from a to b, where it slowly begins to slow until it reaches a steady population.
