A pendulum is released from $\theta_0=60 ^{\circ}$. The rate of change of speed of bob at $\theta=30 ^{\circ}$ is $(g=10 m/s^2)$

Question

$$(a)\;5 \sqrt 3\; m/s^2 \quad (b)\;5\; m/s^2 \quad (c)\;10\; m/s^2 \quad (d)\;2.5\; m/s^2$$