1-3.      Determine the probabilities that the weight  N will fall into the water due to the following two failure modes:  yielding failure of AB and yielding failure of BC.  The diameter of the bars is 8 mm and the yield strength of the bars is  MPa.  Assume  and  are independent.  Neglect the weight of the support rods and indestructible string.  Does this structure need to be redesigned?    (Ans.  )