Five points isn't worth that much tbh, but I'll still help anyways :) that's what the site is for; no need to entice people into doing your problems -- we signed up because we're happy to help!
The graph should look like this:
Days: Cost:
0 120
4 140 (120+20 in admissions)
8 160 (120+40 in admissions)
12 180 (120+60 in admissions)
16 200 (120+80 in admissions)
I hope I helped! ^u^