Let $W$ be the subspace of ${\mathbb R}^4$ spanned by the vectors $$\left[\begin{array}{c} 1\cr 1\cr -1\cr 1 \end{array}\right] \ \mbox{ and } \ \left[\begin{array}{c} -4\cr -6\cr 0\cr -2 \end{array}\right].$$ Find the matrix $A$ of the orthogonal projection onto $W$.
$A=$ $\left[\Rule{0pt}{4.8em}{0pt}\right.$$\left]\Rule{0pt}{4.8em}{0pt}\right.$