What is the unit price (in dollars) at that level of demand?

Question

What is the rate of change of the unit price (in dollars per 1,000 lamps) when the quantity demanded is 4,000 units (x = 4)?

$ 1.  per 1,000 lamps

Answer 1

Do you need the unit price (title question) at x = 4 or the rate of change in the unit price as these are different quantities? Please clarify the question.