I especially need a detailed response as to how to find the increasing and decreasing coordinates, because I’m really confused. Thanks!

(09.01 MC)
The graph below shows the height of a kicked soccer ball f(x), in feet, depending on the distance from the kicker x, in feet:
Graph of quadratic function f of x having x intercepts at ordered pairs 0, 0 and 30, 0. The vertex is at 15, 15.
Part A: What do the x-intercepts and maximum value of the graph represent? What are the intervals where the function is increasing and decreasing, and what do they represent about the distance and height? (6 points)
Part B: What is an approximate average rate of change of the graph from x = 22 to x = 26, and what does this rate represent? (4 points)
(10 points)