The 2.0 -m-long, 15 kg beam in Figure $\mathrm{P} 7.34$ is hinged at its left end. It is "falling" (rotating clockwise, under the influence of gravity), and the figure shows its position at three different times. What is the gravitational torque on the beam about an axis through the hinged end when the beam is at the
a. Upper position?
b. Middle position?
c. Lower position?