Question 3 (15 marks) The beam ABCD shown in Figure Q3 below is pinned at A, supported by two columns fixed at B and C, and has load P applied at D. Columns B and C have cross sectional areas of 2a and a, respectively. Both columns are made of a material with Young's modulus of E. (a) Write down an equilibrium equation for moments about A. (3 marks) (b) Write down the compatibility equation for the system. (3 marks) (c) If load P = 15 kN, calculate the forces in columns at B and C. (9 marks) 0.9m 1.5m 0.8m B C D 4 0.7m 1.2m p Figure Q3