Question: Air pollution the amount of nitrogen dioxide, a brown gas that impairs breathing, present in the atmosphere on a certain may day in the city of long beach, is approximated by
A(t) = 136 + 28 (0 ≤ t ≤ 11)
1 + 0.25(t - 4.5)2
Where a(t) is measured in pollutant standard index (psi) and t is measured in hours, with t = 0 corresponding to 7 a.m. When is the psi increasing and when is it decreasing? At what time is the psi highest, and what is its value at that time?