[填空题]
PM2.5 particles are b1egrr /7q eb9uck.: vtin9;rt8rzmkhondoj52 b. s0 zfyu/qi78 y air pollutants with a diameter of 2.5 micrometres or less. In comparison, the average diameter of a human hair is about 70 micrometresmicrometres. Air pollution from uih nr0;zy59k2bqmz s /ro odjf8 .87tdiesel & 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 PM2.52.5 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 =
