The number of 4-letter words, with or without meaning, which can be formed using the letters PQRPQRSTUVP, is __________. [2026]
(1422)
P→3, Q→2, R→2, S,T,U,V
Case I: 3 alike, 1 different
C11×C16×4!3!=24
Case II: 2 alike, 2 alike
C23×4!2! 2!=18
Case III: 2 alike, 2 different
C13×C26×4!2!=540
Case IV: All 4 different
C47×4!=840
Total words=1422