
Answer:
a) -2t²+12t+15   b) 25, 31  c) 26
Step-by-step explanation:
a) To find out rate, we will take derivative of the given equation
dN/dt= -2t2+12t+15
b) At 9 am , it will be 1hr since the start of morning shift so t=1
dN/dt= -2(1)²+12(1)+15
dN/dt=25
At 10 am, it will  2 hrs since the start of morining shift be so t=2
dN/dt=-2(2)²+12(2)+15
DN/dt= 31
c) N(2)-N(1)= (-(2)³+6(2)²+15(2))-(-(1)³+6(1)²+15(1))
        =(46)-(20))
        = 26