We have III, TT, D, S, R, B, U, O, N
Number of words with selection (a, a, a, b)
=‌8C1×‌=32Number of words with selection (a, a, b, b)
=‌=6Number of words with selection (a, a, b, c)
=‌2C1×‌8C2×‌=672Number of words with selection (a, b, c, d)
‌=‌9C4×4!=3024‌∴‌ total ‌=3024+672+6+32‌=3734