If $\vec{a},\vec{b}and\vec{c}$ are non-coplanar vectors, prove that the four points $2\vec{a}+3\vec{b}-\vec{c},\vec{a}-2\vec{b}+3\vec{c},3\vec{a}+$ 4$\vec{b}-2\vec{c}and\vec{a}-6\vec{b}+6\vec{c}$ are coplanar.

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