. A single crystal of zinc is oriented for a tensile test such that its slip plane normal makes an angle of 65° with the tensile axis. Three possible slip directions make angles of 30°, 48°, and 78° with the same tensile axis. (Total Points: 5) (a) Which of these three slip directions is most favored? Why (please show reasoning and calculations)? (Points: 2) (b) If plastic deformation begins at a tensile stress of 2.5 MPa (355 psi), determine the critical resolved shear stress for zinc. (Points: 3)