Answer:
a) -15 unites per dollar
b) -12 units per dollar
c) -18 units per dollar
Step-by-step explanation:
We are given the following in the question:

where N(p) is the number of boxes of nails at p dollars per box.
a) average rate of change of demand for a change in price from $2 to $3.
Average rate of change =

b) instantaneous rate of change of demand when the price is $2
Instantaneous rate =


The instantaneous rate of change of demand when the price is $2 is decreasing at 12 units per dollar.
c) instantaneous rate of change of demand when the price is $3
Instantaneous rate =

The instantaneous rate of change of demand when the price is $3 is decreasing at 18 units per dollar.