Answer:
The demand of the desk is 4000 units
Explanation:
From the question we know that p is equals negative x squared plus 23, that can be written as:

Where p is the unit price and x represent the quantity demanded in thousands. Replacing p by 7 and solving for x, we get:

Since x is given in thousands of units, if the price is $7, the demand of the desk is 4000 units.