[填空题]
PM2.5 particles are tiny air pollfmui+. hu( 7m19k istyq:7 qieutants with a diameter of 2.5 mi-5q9x+c -qxudub-gy32 rl xwycrometres or less. In comparison, the average diameter of a human hair is about 70 micrometrc -xgur+-dwxqqy92 -ubyl3 5xesmicrometres. Air pollution from diesel & petrol engines form part of PM2.5 emissions and of particularparticular concern due to the health impacts.
During a particular working day, the rate of PM2.5 emissions, in grams per second, from all road vehicles in Beijing, China is modelled by the function
E(t)=6sin($\frac{π}{6}$t−$\frac{5π}{6}$)+9,0≤t≤24,
where t is the elapsed time, in hours, since midnight.
1.Find the maximum rate of PM2.5 emissions during the day in Beijing, China.$E_{max}$ = g/sec
2.Find the times at which the maximum rate of PM2.5 emissions occur during the day. t =
