a) Since the relation is proportional, the graph is a line.
In order to graph a line we only need two points and connecting them we get the line.
In this case, we know that at 4h the pool has 5200 gallons. The point woud be (4, 5200)
Now we need another point. The simplest one is the origin. When the time is zero, the amount of water in the pool is also 0, then we have another point (0, 0)
Now with the points (0, 0) and (4, 5200) we can graph the relationship.
b) We need to compair the filling rates. In the graph provided we can see that in 3 hours, there is 10,800 gallons. Since the other pool had 5,200 gallons in 4 hours, is clear that the second pool fills much more quicker.