P$\mathrm{.}3.(25$ points$)$ For the truss with a $3$ kN applied force, use the method of joints to determine the force developed in each member. Indicate whether each member is in tension or compression $($check the corresponding box$).$

$Fy=0,RA+R=0$

$Fx=0,RCH-3=0$

$RCH=3$