Answer
(a) $\tau = 86.6~m\cdot N$
(b) She could exert more torque by using toe straps to pull one pedal up with the muscles of one leg while pushing down with her weight and the muscles of her other leg.
Work Step by Step
(a) She exerts maximum torque when the direction of her weight makes a right angle with the axis of rotation. In that case, $sin(\theta) = 1$.
$\tau = r~F~sin(\theta) = r~mg$
$\tau = (0.17~m)(52~kg)(9.80~m/s^2)$
$\tau = 86.6~m\cdot N$
(b) She could exert more torque by using toe straps to pull one pedal up with the muscles of one leg while pushing down with her weight and the muscles of her other leg.
