Problem$-4$:

$15\mathrm{.}97$ At the instant shown, the velocity of collar $A$ is $0\mathrm{.}4\frac{m}{s}$ to the right and the velocity of collar $B$ is $1\frac{m}{s}$ to the left. Determine $(a)$ the angular velocity of bar $AD,($b$)$ the angular velocity of bar $BD,($c$)$ the velocity of point $D.$

Fig. P$15\mathrm{.}97$