$15\mathrm{.}52$ Arm ACB rotates about point $C$ with an angular velocity of $40ra\frac{d}{s}$ counterclockwise. Two friction disks A and $B$ are pinned at their centers to arm ACB as shown. Knowing that the disks roll without slipping at surfaces of contact, determine the angular velocity of $(a)$ disk $A,(b)$ disk $B.$

Fig. P$15\mathrm{.}52$