For a)
The y-intercept of the graph is the value of y-coordinate when x=0
in this case, the y-intercept is 80
For b)
in the context of this situation, the y-intercept is the initial height of the ball at 0 sec
For c)
the maximum height is the vertex of the parabola as we can see in the graph the maximum height is 144 at 2 seconds
For d)
as we said in the last subsection the maximum height is 144 ft
For e)
as we can see in the graph the parabola reach y=0 at x=5 in order words the ball reaches the surface of the river in 5 seconds
the point in red is the maximum height and the time that the ball reaches this height
the initial height is in blue, at time=0sec
and the time that the ball reaches the surface of the rive is in green the height in this case is 0