Before we draw the graph, let's calculate the cost at different amount of movies watched.
1 Movie = 8
2 Movie = 2 * 8 = 16
3 Movie = 3 * 8 = 24
4 Movie = 4 * 8 = 32
5 Movie = 5 * 8 = 40
6 movie = total 40 (no additional charge)
7 movie = total 40 (no additional charge)
.
.
.
16 movie = total 40 (no additional charge)
Thus,
From 0 - 5 movies the graph will be linear with 8 units increase (dollars) PER movie
Then from 5 movie onwards to 16 movies the cost will be same ($40), so that would be a horizontal line at y = 40 [from x = 5 to x = 16]
The graph can look something like this: