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If N denotes the number of ways of s...

If `N` denotes the number of ways of selecting `r` objects of out of `n` distinct objects `(rgeqn)` with unlimited repetition but with each object included at least once in selection, then `N` is equal is a. `.^(r-1)C_(r-n)` b. `.^(r-1)C_n` c. `.^(r-1)C_(n-1)` d. none of these

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