As shown, a truss is loaded by the forces $P1=2\mathrm{.}21kN$ and $P2=0\mathrm{.}910kN$ and has the dimension $a=3\mathrm{.}10m$

a$)$ Determine $F_{BC},$ the magnitude of the force in member $BC,$ using the method of joints.

b$)$ Determine $F_{CG}$ and $F_{GH},$ the magnitudes of the forces in members $CG$ and $GH,$ respectively using the method of joints.