Find a basis of the eigenspace associated with the eigenvalue $-3$ of the matrix $$A = \left[\begin{array}{cccc} -2 &0 &1 &2\cr -2 &-3 &10 &8\cr 1 &0 &-5 &-1\cr -1 &0 &5 &1 \end{array}\right].$$ A basis for this eigenspace is