3．The points \(A , B , C , D\) and \(E\) are five of the vertices of a rectangular cuboid and \(A E\) is a diagonal of the cuboid．With respect to a fixed origin \(O\) ，the position vectors of \(A , B , C\) and \(D\) are \(\mathbf { a , b , c }\) and d respectively，where $$\mathbf { a } = \left( \begin{array} { c } 1
2
- 1 \end{array} \right) , \quad \mathbf { b } = \left( \begin{array} { c } 0
- 3
- 8 \end{array} \right) , \quad \mathbf { c } = \left( \begin{array} { c }