A uniform horizontal plank 2.0 m long is hinged at its center. A 30 N force acts downward at the right end, perpendicular to the plank. At the left end, a force of magnitude F is applied in a direction that makes an angle of 30° above the plank, lying in the same vertical plane. If the net torque about the hinge is zero, what is the magnitude of F?
a) 30 N
b) 60 N
c) 34.6 N
d) 120 N