4 The grain of a wooden member forms an angle of \( 15^{\circ} \) with the vertical. The state of stress for a point is given. (a) Determine the in-plane shearing stress parallel to the grain. (6 points) (b) Determine the normal stress perpendicular to the grain. (4 points) (c) Show above results on the sketch of the oriented elements. (4 points) (d) Plot Mohr's circle and mark the original element and the oriented element on the circle. (6 points)