Answer
(a) 21
(b) 2520
(c) 720
Work Step by Step
(a) $\frac{7!}{2!5!} = 21$ sequences are possible.
(b) $\frac{7!}{2!1!1!1!1!1!} = 2520$ sequences are possible.
(c) $6! = 720$ sequences are possible.
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