The sandbox must be filled with sand. The sandbox has a depth of 2ft and a diameter of 14ft.

Assuming the sandbox is a circle isnce you gave diameter

volume=area of base times depth

area of base=circle

circle=pi r^2

r=d/2

d=14

r=14/2

r=7

circle=pi7^2

circle=49ipi

volume=2 times 49pi

volume=98pi ft^3

if we aprox pi to 3.14 then

98 times 3.14=279.46 ft^3