Permutations and Combinations

4 letter words from
ACCOMMODATION
There are different letters
"ACCOMMODATION"
namely,
A, C, D, I, M, N, O, T
2‌2‌1‌1‌2‌1‌3‌1
Case ( 1 ) all 4 letters of the word are different numbers of combinations
=‌8c4=70
Case (II) 2 letters are same and 2 are different.
=‌4c1⋅‌7c2−6=78
( ∵ when we select 2 same letter from 0 and 3rd letter also from, 0 then this need to be subtracted and such cases are 6 )
Case (III) When 3 letters are same
=1.‌7c1=7
Case (IV) When 2 letters are same and other 2 are also same.
=‌4c1×‌3c1=12
Hence, total number of combination
=70+78+7+12=167