16.—受力系統如右圖所示,試計算斷面B處之剪 力及彎矩(VB,MB)為何?(A) (-4.8 tf,58.6 tf-m) (B) (-5.2 tf,56.4 tf-m )(C) (-5.8 tf,52.8 tf-m ) (D) (-6.4 tf,50.6 tf-m )