Question $4$: The crank $(AO)$ and connecting rod $(AB)$ of a theoretical steam engine are $200$ mm and $700$ mm long respectively. The crank rotates at $120r.p.m.$ in the clockwise direction with uniform elocity. Answer the following:

$($a$)$ Is the system shown in the figure below a mechanism or a structure? $V^2=re\frac{d}{60}$

$($b$)$ Draw the position diagram.

$($c$)$ Draw the velocity diagram and find the velocity of the piston $\text{'}B\text{'}($marks $=2+2+3)$