Cable tray multiconductor calculation

[ramihamdan]

What is the cable tray size, using nec 2008 table 392.9?
This is a NEC question from an exam prep site.

 

[ron]

Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allow-able fill area resulting from the calculation in Column 2of Table 392.9 for the appropriate cable tray width. The4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them.