question: Determine the vertical displacements at A of the pin-connected  structure in Figure P9.31. Given: E = 200 GPa,  AAB = 1000 mm2 , and AAC = AAD = 500 mm2 . <image 1>
  Options: A: 4.32 mm, B: 4.12 mm, C: 4.22 mm, D: nan