Can someone help me? The graph shows the distance, y, in miles, of a moving train from a station for a certain period of time, x, in hours:

A graph titled Distance Vs Time is shown with Time in hours labeled on x-axis and Distance from Station 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, 50, 100, 150, 200, 250, 300, 350, 400. The graph shows a straight line joining the ordered pairs 0, 100, and 1, 150, and 2, 200, and 3, 250, and 4, 300.

What is the speed (in miles per hour) of the train?

100 miles per hour
50 miles per hour
150 miles per hour
400 miles per hour