BASE
If BUST - 1, LUST - 1 and LAST - 1 then it must be one of --ST. If not --ST then BU--, LU-- and LA can not all score 1.
Using the above logic for --ST - 1
If BASE - 1 then --S- since not ---E from BLUE - 0
If BASE - 0 then ---T
--EDIT--
gah you posted while I was typing...