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) = 136/1+ 0.24(t − 4.5)^2 + 28 (0 ≤ t ≤ 11) where a(t) is measured in pollutant standard index (psi) and t is measured in hours, with t = 0 corresponding to 7 a. m. determine the time of day when the pollution is at its highest level.

(50 ) mrs. julien’s and mrs. castillejo’s classes are selling cookie dough for a school fundraiser. customers can buy packages of macadamia nut chip cookie dough and packages of triple chocolate cookie dough. mrs. julien’s class sold 25 packages of macadamia nut chip cookie dough and 30 packages of triple chocolate cookie dough for a total of $221.25. mrs. castillejo’s class sold 5 packages of macadamia nut chip cookie dough and 45 packages of triple chocolate cookie dough for a total of $191.25. (a) write the system of equations that model the problem. be sure to explain which equation represents which situation. (b) find the cost of each type of cookie. show your work. (c) explain which method you used to solve the system and why you chose that method.