$4\mathrm{.}29$ The spanner shown is used to rotate a shaft. A pin fits in a hole at $A,$ while a flat, frictionless surface rests against the shaft at $B.$ If a $300-N$ force $P$ is exerted on the spanner at $D,$ find $(a)$ the reaction at $B,(b)$ the component of the reaction at $A$ in a direction perpendicular to $AC.$

$4\mathrm{.}30$ The spanner shown is used to rotate a shaft. A pin fits in a hole at $A,$ while a flat, frictionless surface rests against the shaft at $B.$ If the moment about $C$ of the force exerted on the shaft at $A$ is to be $90N*m,$ find $($a$)$ the force $P$ that should be exerted on the spanner at $D,(b)$ the corresponding value of the force exerted on the spanner at $B.$

Fig. P$4\mathrm{.}29$ and P$4\mathrm{.}30$