Knowing that the sphere is circumscribed by the cube with given edge length, we may find the volume of the sphere. First notice that the length of the side of the cube will coincide with the length of the diameter of the sphere. We therefore can say that edge=diameter.. Volume of the sphere is defined by the formula:
V =  \frac{4}{3}  \pi  r^3
and we know that radius is just 1/2 of the diameter and diameter in this case is 4 therefore r=2. substituting the value for 'r' in the formula you'll have:
V =  \frac{4}{3}  \pi (2^3)
V = 33.51 cu. units