By multiplying the three length dimensions together, you get a volume. If you multiply volume by (cost per unit volume), you get cost.
You didn't specify, but if your length measurements above are in feet, then you just calculate 54 14 8 28. If your measurements are in inches, you need to divide this first calculation by twelve (inches per foot) for each time you use inches (three). That means 54 14 8 28 12 12 12.
Hope this helps,
Stephen La Rocque.