Trish is ordering t-shirts from a website that charges a certain amount per t-shirt plus a flat rate for shipping. The cost for a given number of t-shirts is shown in the table.

20a. Write an equation to represent the situation. (Write your answer with no spaces, all lowercase letters, and write the slope as a decimal)

20b. What does the slope mean in the context of the situation?

20c. What does the y-intercept mean in the context of the situation?