1. emily filled an empty horse trough with water. the water level, in centimeters, is proportional to time elapsed, in minutes, since she began filling the trough. the graph shows this relationship.(a) what rate does the point 8,28 represent? explain.(b) what is the unit rate for the situation in terms of centimeters/minute? explain.(c) explain how the points 8,28 and 6,21 show that the water level varies directly with the time elapsed.