The volume of this prism would be 294 cubic units.
To determine this you can use the given perimeter of 28 to create combinations of dimensions of a recatangule prism.
I started with 7 + 7 + 7 + 7 to get 28. This means the length and width were both 7 units.
This would make the dimensions of this prism 7 x 7 x 6(the height).
The find the volume multiply all three numbers.
The volume is 296 cubic units.