Orthogonality & Least Squares · Medium problem

The vectors $\mathbf v_1 = (1,2,1)$ and $\mathbf v_2 = (2,-1,3)$ are not orthogonal. Apply Gram–Schmidt to replace $\mathbf v_2$ with $\mathbf w = \mathbf v_2 - \operatorname{proj}_{\mathbf v_1}\mathbf v_2$, then write $\mathbf b = (8,1,11)$ as $\mathbf b = c_1\mathbf v_1 + c_2\mathbf w$ (now an orthogonal pair). Find $c_2$.