Royce is taking violin lessons. The instructor charges an initial fee and an hourly fee. The amount Royce pays is based on the length of his lesson is shown on the graph below. What is the instructor's hourly fee?

sample answer: you can determine whether each element of the domain is paired with exactly one element of the range. for example, if given a graph, you could use the vertical line test; if a vertical line intersects the graph more than once, then the relation that the graph represents is not a function.