It is given in the question that
The revenue (in thousands of dollars) from producing x units of an item is modeled by
[tex]R(x)=12x-0.01x^2[/tex]
a. Average rate of change is given by
[tex]\frac{R(1007)-R(1002)}{1007-1002}[/tex]
[tex]= \frac{1943.51-1983.96}{5}[/tex]
[tex]=\frac{-40.45}{5} = -8.09[/tex]
So the average rate of change of revenue is -8090dollars per unit .
b .To find the marginal revenue, we have to differentiate revenue function, that is
[tex]R'(x)=12-0.02x[/tex]
And at x=1000, we will get
[tex]R'(1000) = 12-0.02(1000)=-8[/tex]
S the marginal revenue is -8000 dollars.