A civil engineering model for WW, the weight (in units of 1000 pounds) that a bridge can withstand without sustaining structural damage is normally distributed. Suppose that for a certain bridge WN(400,40²). Suppose further that the weight of cars traveling on the bridge is a random variable with mean 2.5 and standard deviation 0.25. Approximately how many cars would have to be on the bridge simultaneously to have a probability of structural damage that exceeds 0.1?

Hint 1: Sums and differences of normal random variables are normal. Hint 2: When you get to a quadratic inequality/equation in n, use an online quadratic equation solver and take the minimum positive value which results.

Approximately _____________ cars (round to an integer number).