The graph shows the depth, y, in meters, of a shark from the surface of an ocean for a certain amount of time, x, in minutes:

a graph is titled distance vs. time is shown. the x axis is labeled time in minutes and shows numbers 0, 1, 2, 3, 4, 5. the y axis is labeled distance from ocean surface in meters. a straight line joins the points c at ordered pair 0,66, b at ordered pair 1, 110, a at ordered pair 2, 154, and the ordered pair 3, 198.

part a: describe how you can use similar triangles to explain why the slope of the graph between points a and b is the same as the slope of the graph between points a and c. (4 points)
part b: what are the initial value and slope of the graph, and what do they represent? (6 points)