Tanisha owns a wallpaper hanging business. Her charge, C, for hanging wallpaper is $40 plus $0.30 per square foot of wallpaper she hangs, or C = 40 + 0.30s, where s is the number of square feet of wallpaper she hangs.

(a) Graph C = 40 + 0.30s, for s ‰¤ 500.

(b) From the graph, estimate her charge if she hangs 300 square feet of wallpaper.

(c) If her charge is $70, use the equation for C to determine how many square feet of wallpaper she hung.