Extracted text: A lever is attached to a shaft with a square shear key as shown. The force applied to the lever is P-250 N. If the shear stress in the key must not exceed 85 MPa, determine the minimum dimension "a" that must be used if the key is 15 mm long. Shear key 200 mm 42 mm Shear key detail O 7.05 mm O 9.12 mm O 654 mm O 5.45 mm O 467 mm