i'm stuck on the line for printf("Data: $%4.2f\n", 30+(y-2)*5);.

you can ignore the lines below this because it is just wrong

ok, so i'm suppose to create this program that tells the customers how much they pay for their phone. For the data plan, I am suppose to create a line that shows them how much they spend on the data plan. Customers pay 30$ for the first 2.0GB, then they pay 10$ for every GB or fraction thereof. I don't know how to create a line for this! (or I just suck at math ) Anyway, please help me!