Does order matter? Do you consider [OBO], [OOB], and [BOO], as 1 choice or as 3 choices? We must know whether they are considered different or all the same. If it is one choice then there are only 5 ways: {B,O,O}, {I,O,O}, {L,O,O}, {G,O,O}, and {Y,O,O} If it is three choices then there are 15 ways: BOO, OBO, OOB, IOO, OIO, OOI, LOO, OLO, OOL, GOO, OGO, OOG, YOO, OYO, OOY. Edwin