The aged dependency ratio is defined as the number of individuals age 65 or older per 100 individuals ages 20–64. The aging of the baby boomer generation along with medical advancements and lifestyle changes for all individuals have caused this ratio to rise, shaping society’s plans for the needs of a greater number of older individuals. By using Social Security Administration data for selected years from 1990 and projected to 2045, the aged dependency ratio can be modeled by the function 

A(t) = -0.000497t³ + 0.0449t² - 0.669t + 22.3

where t is the number of years past 1990.

(a) Find the critical points for this model, and classify them as relative maxima or relative minima.

(b) Interpret the points found in part (a)