A ball of mass $1\,\text{kg}$ moving with velocity $\vec{v} = 3\hat{i} + 4\hat{j}\,\text{m/s}$ collides with a smooth wall and after collision moves with velocity $\vec{v}' = -2\hat{i} + 6\hat{j}\,\text{m/s}$. Which of the following unit vectors is perpendicular to the wall?