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A student council consists of three freshmen, four sophomores, four juniors, and five seniors. How many committees of eight members of the council contain at least one member from each class?

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DEFINITIONS

Multiplication rule: \textbf{Multiplication rule: }If an operation consists of kk steps, where the first step can be performed in n1n_1 ways, the second step can be performed in n2n_2 ways, ... and the kkth step can be performed in nkn_k ways, then the operation can be performed in n1n2...nkn_1n_2...n_k ways.

Definition permutation\textbf{permutation} (order is important):

P(n,r)=n!(nr)!P(n,r)=\dfrac{n!}{(n-r)!}

Definition combination\textbf{combination} (order is not important):

C(n,r)=(nr)=n!r!(nr)!C(n,r)=\left(\begin{matrix}n\\ r\end{matrix}\right)=\dfrac{n!}{r!(n-r)!}

with n!=n(n1)...21n!=n\cdot (n-1)\cdot ...\cdot 2\cdot 1.

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