Looks good.
By the way 4d-volume wouldn't be too hard to calculate:
The 2D-volume of a square is V₂ = A = a².
The 3D-volume of a cube is V₃ = a³.
→The 4D-volume of a tesseract is V₄ = a⁴.

Although its so counterintuitive to make sense of these higher dimensions, the math of it is mostly as easy as for the lower dimensional counterpart.