$17.$ For a four$-$bar mechanism, shown in Fig. determine the acceleration of C and angular acceleration of link $3$ when crank $2$ rotates at $20$ radians per second. $(20$ Marks$)$

$18.$ In a four$-$bar mechanism $\backslash (\backslash$mathrm$\{$ABCD$\},\backslash$mathrm$\{$AD$\}\backslash )$ is fixed link of $120$ mm long. The crank AB is $30$ mm and rotates at $100$ rpm clockwise while $\backslash ($ C D$=60\backslash$mathrm$\{$~mm$\}\backslash )$ oscillates about $\backslash (\backslash$mathrm$\{$D$\}.\backslash$mathrm$\{$BC$\}\backslash )$ and $\backslash ($ A D $\backslash )$ are of same length. Find the angular velocity of link $\backslash ($ C D $\backslash )$ when angle $\backslash ($ B A D$=60^\{\backslash$circ$\}\backslash )$ by relative velocity method.