b) c = b3.99 + 4.95
c is the total cost, 4.95 is a constant fee that you have to pay for the monthly service, so that will always be there. b3.99 will vary depending on how many books are downloaded.
c) I can't really graph now I'm sorry, I don't know if this graph should be accurate or not but If you want it very accurate then you're gonna have a y-intercept (x = 0) at 4.95 And you're gonna wanna go up 3.99 units each x unit, so at (x=1) you must be at y= 4.95 + 3.99 = 8.94
If you don't want it extremely accurate then you can just make the y-intercept at 5 and you can go up 4 units each x unit.