For the plane stress situation shown in the figure, the maximum shear stress and the plane on which it acts are:

1. $-50$ MPa, on a plane $45^{\circ}$ clockwise w.r.t. $x$-axis
2. $-50$ MPa, on a plane $45^{\circ}$ anti-clockwise w.r.t. $x$-axis
3. $50$ MPa at all orientations
4. Zero, at all orientations