Answer:
The answer is B.
Explanation:
The formula is;

Maximum value of the function is where the x value makes (x-6)^2 equals to 0. Then;

Breaking point of the function is x=6. When we put 6 instead of x, the function will go to:

When we put x=4, the function will go to;

Then the solution is increasing: x < 6; decreasing: x > 6
Also check the graph at the attachment.