Why is the answer for letter b 9?

Step-by-step explanation:

From x=0 to x=1, the function is above the x-axis, so the area is positive.

From x=1 to x=5, the area above the x-axis is greater than the area below the x-axis, so the net area is positive.

From x=5 to x=9, the area above the x-axis is greater than the area below the x-axis, so the net area is positive.

Since the area increases in each interval, the area is a maximum at x=9.