1-5.      A block that has a normally distributed weight  N is held in place on an incline by a rope as shown.  If the yield stress of the rope also follows a normal distribution  MPa, what is the minimum diameter that the rope must have so that the block will not break free if the probability of failure must be less than 10^-4?  Assume  and are independent variables and .  Neglect friction.    (Ans.  mm)