Figure $4$ is a front elevation view of a simple truss that supports vertical loads at nodes $C$ and $D.$ All of the truss members have cross section properties $AE.$

$[4$a$](5$ pts$).$ Compute the support reactions and distribution of forces throughout the structure.

$[4$b$](5$ pts$).$ Use the method of virtual forces to show that the total deflection at node $C$ is:

$=\frac{PL}{AE}[\frac{8\sqrt[\phantom{2}]{10}}{3}]$