Customers at the gym pay a membership fee to join and then a fee for each class they attend. Here is a graph that represents the situation. What does the vertical intercept mean in this situation?

(Picture in attachments)

A. The customer pays 60 dollars for the membership fee.

B. The customer pays 20 dollars for each classes.

C. The customer pays 20 dollars for the membership fee.

D. The customer pays 60 dollars for each classes.