Explanation:
The cost function for this industry is given by,


When it is used for full 8 hours, total cost is

When it is used for 7 hours, TC is $600.
When it is used for 6 hours, TC is $550
When it is used for 5 hours, TC is $500.
When it is used for 4 hours, TC is $450.
When it is used for 3 hours, TC is $400.
When it is used for 2 hours, TC is $350.
When it is used for 1 hours, TC is $300.
When it is used for 0 hours, TC is $250.
Thus, the cost curve will look like the diagram given below.