The graph shows the distance, y, in miles, of a moving motorboat from an island for a certain amount of time, x, in hours: A graph titled Distance Vs. Time is shown with Time in hours labeled on x axis and Distance from Island in miles labeled on y axis. The scale on the x axis shows the numbers 1, 2, 3, 4, 5, 6, 7, and the scale on the y axis shows the numbers 0, 35, 70, 105, 140, 175, 210, 245, 280, 315. The graph shows a straight line joining the ordered pairs 0, 35, and 1, 105, and 2, 175, and 3, 245, and 4, 315.
What is the speed of the motorboat? (5 points)

Group of answer choices

315 miles per hour

70 miles per hour

35 miles per hour

105 miles per hour