#### Answer

A 3D space that is contained by planes z=0 and z=6 (inclusive).

#### Work Step by Step

With no x- or y- limitations, we are looking at an area that would encompass all values of x- and y- so long as the z-value of those points fall between planes z=0 and z=6.
Conceptually, think of the two given z-planes "sandwiching" all the space between them.