This is actually an area problem:
The diameter of the circle is 6 which is the width of the sandbox and the radius is 1/2 of the diameter so r=3
Formula for area= π(r^2) or pi*radius squareThe area of the circle would be 9π which is 28.27
Then you subtract it from the area of the sandbox which is 6*10=60
60-28.27=31.73 which rounds to 32 square feet
Answer: C