What is the topic of the text above?

I - The text explains the concept of production costs.
II - The text presents examples of fixed and variable costs.
III - The text shows how to calculate the total cost of production.
IV - The text explains the concept of long-term costs.
a) I and II are correct.
b) II and III are correct.
c) I, II, and III are correct.
d) I, II, III, and IV are correct.