The shaft at O drives the arm OA at a clockwise speed of 90 rev/min about the fixed bear...

The shaft at O drives the arm OA at a clockwise speed of 90 rev/min about the fixed bearing at O. Use the method of the instantaneous center of zero velocity to determine the rotational speed of gear B (gear teeth not shown) if (a) ring gear D is fixed and (b) ring gear D rotates counterclockwise about O with an angular speed of 80 rev/min.