Problem $5$: a$)$ Boom $BD$ is held up by a continuous cable that runs from A through an eyelet at $B$ to $C.$ The cable is attached to the wall via hooks at A and $C.$ Denote as $T_{BC}$ the force applied by cable $BC$ on member $BD.$ Determine the magnitude of the projection of $T_{BC}$ along line $AB.$ The tension in the cable is $5$ kN $.$