3. Find and draw all the spanning trees of the following graphs. You have to list all the spanning trees to get full points for each subproblem. Otherwise, you get 0 points.
42. 若鋼筋混凝土採用矩形梁斷面寬度為30cm,有效深度為50cm,混凝土強度為 f c ' = 280kgf/cm2 ( ),鋼筋強度為fy=4200 kgf/ cm2,則對於最小鋼筋量 為何? (A) 最小鋼筋量等於4.781 cm2 (B) 最小鋼筋量等於5.000 cm2 (C) 最小鋼筋量等於5.214 cm2 (D) 最小鋼筋量等於5.318 cm2