For the four$-$bar linkage shown, the angular velocity and th angular acceleration of the drive link $OA$ are $10ra\frac{d}{s}$ and $ra\frac{d}{s^2},$ both counterclockwise. Determine the angular acceleration of bars $AB$ and $BC$ for the instant represend $,$ its asking for angular acceleratins not angular velocities, please take it step by step when substituting into the accelaeration analysis equation