In the figure, the rigid and massless rod is suspended by $3$ elastic cables and is under the influence of

temperature and external load. Extension stiffness and thermal expansion coefficient are the same for all three

elastic rods.

a$)$ Calculate the axial loads on the cables when AT is $0.$

b$)$ Calculate the axial loads on the cables when $F$ is $0.$

c$)$ as $F10kN,AT=0,I=2m,a=6m,E=200$GPa and oem $=120$Mpa

Calculate the safe cross$-$sectional area for the cables, if known. Calculate the total displacement

of the system based on the calculated area. $($Axial load $+$ temperature effect$)$