To find the orthogonal projection of $v = (0,0,5,0)^T$ onto the subspace $W$ spanned by $(-1,-1,-1,1)^T,(-1,1,1,1)^T,(-1,-1,1,-1)^T$.
Since the vectors which forms a basis for $W$ are already orthogonal, the orthogonal projection of $v = (0,0,5,0)^T$ onto the subspace $W$ is the sum of the projection of $v$ on each of the basis vectors.
Is my logic and method correct?