use '?' for JOKER (blank)

From letters X, Y, S, T, U, S  I made following words

6 letter words

xystus[16]

5 letter words

xysts[15]

4 letter words

xyst[14]

3 letter words

tux[10], sty[6], uts[3]

2 letter words

xu[9], us[2], ut[2]