Civil engineers believe that w, the amount of weight (in units of 1000 pounds) that a certain span of a bridge can withstand without structural dam- age resulting, is normally distributed with mean 400 and standard deviation 40. suppose that the weight (again, in units of 1000 pounds) of a car is a random variable with mean 3 and standard deviation .3. approximately how many cars would have to be on the bridge span for the probability of structural damage to exceed .1?