The answer should be C 20
Answer:

And on this case we can use the product rule for a derivate given by:

Where
and
And replacing we have this:

Step-by-step explanation:
We assume that the function of interest is:

And on this case we can use the product rule for a derivate given by:

Where
and
And replacing we have this:

Since each ton equals 2000 pounds you add 2000+2000+500 (because of the half) and it equals 4,500 pounds