A uniform rigid rod of length $L$ is pivotally attached to a vertical wall at its lower end. The rod is held at an angle $\theta$ relative to the wall. A student applies a constant force of magnitude $F$ to the free end of the rod. The force vector is oriented at an angle $\phi$ relative to the vertical wall, where $\theta > \phi$, as shown in the figure. Which of the following expressions correctly represents the magnitude of the torque exerted by the student's force about the pivot?