At the instant shown, the wheel rotates with an angular velocity of $=15\mathrm{.}6ra\frac{d}{s}$ and an angular acceleration of $=7\mathrm{.}8ra\frac{d}{s^2}.($Figure $1)$

Part A

Determine the angular acceleration of link $BC$ at the instant shown measured counterclockwise.

Express your answer using three significant figures. Enter positive value if the angular acceleration is counterclockwise and negative value if the angular acceleration is clockwise.