[填空题]
Particulate Matter (PM) is a measure of air pollution. PM2.5 ct *o b+(gq2.y nsor:)b,wt)wcxxf n;ooncentrationl(ugcjq.4 .ue9r q55 t8 lsiuu, measuu(8i q.u5l5ej cgtulu 4s9.qrred in $\mu \mathrm{g} / \mathrm{m}^{3}$ , is a measure of the amount of fine, inhalable particles with diameters of 2.5 micrometres or smaller in the air. The PM2.5 levels were measured at various times on a particular day in Delhi, India, with the results shown in the table below. The max and min PM2.5 levels were recorded and are are included in the data.
1. Determine an appropriate model for the PM2.5 concentration, P , in terms of the number of hours after midnight, t .
On this particular day, the Central Pollution Control Board of Dehli alerts citizens that the air quality will be "very poor" between 09:15 to 10:15 and recommends that the citizens should minimise being outside during these times of the day.$P(t)=a \sin (b-c)+d$ a = b = c = d =
2. Use your model from part (a) to estimate the PM2.5 level that the Central Pollution Control Board considers to be "very poor".$\approx$ $\mu \mathrm{g} / \mathrm{m}^{3}$
