5. A sign structure has pin supports at A and C which are 2 m apart. Members AB and BC are steel bars pin connected at joint B. The length of BC is 3m. A sign weighing 5.4 kN is suspended from bar BC at points D and E. Find the cross-sectional area of AB and the diameter of pin at C if the allowable stresses in tension and shear are 125 MPa and 90 MPa respectively. 2.0 m C 0.8 m 0.9 m 0.9 m E B 0.4 m W=5.4 kN