Answer:
2 pounds of reduction per pollutant per day
Step-by-step explanation:
Cost of controlling emissions  :  C(q)  =  4000 + 100*q
And govermment subside is 400 * q
Therefore the cost function is:
C(q) =  4000 + 100q² - 400q
Derivative of C(q)  ⇒ C´(q)  =  200q - 400
equalizing to cero   200*q - 400 = 0  ⇒  q  = 400/200  q = 2
If we take second derivative  C¨¨(q)  = 200     200> 0  there is a minimun in the poin q = 2