At a point within a body subjected to two mutually perpendicular directions, the stresses are $100$ N$/$mm$2$ tensile and $30$ N$/$mm$2$ compressive. Each of the above stresses is accompanied by a shear stress of $50$ N$/$mm$2.$ Determine the normal stress, shear stress and resultant stress on an oblique plane inclined at an angle of $200$ with the normal.