Playing MP3 Files

When I play MP3 files that are encoded at a Variable Bit Rate, UltraPlayer does not display a Bit Rate (kbps) for these files. Why?
Files that are encoded at a Variable Bit Rate (VBR) do not have a constant bit rate that can be displayed in the "kbps" field. Only files encoded at a Constant Bit Rate (CBR) will display "kbps" in UltraPlayer.