Hi, thank you for posting your question here at Brainly.
Since the hedge is surrounding the square base, the area of the base can be determined by subtracting the area of the base from the hedge.
A = pi*r^2 - (4x)^2
A = pi*(6x)^2 - (4x)^2
A = 2x^2*(3pi - 2)
I hope I was able to answer your question. Have a good day.