This question's solution is based on two context. First off, the probability of any events or occurrence cannot be greater than 1. If the question demands finding the probability that the proportion of all thickness (X) is less than 1.5 given the available data (mu and rho) then that would practically be impossible. It would only be feasible to ask, "if it were less than 1" My point is, suppose X is 1.3 which is actually less than 1.5, then we have a contradiction because our probability of occurrence or non-occurrence cannot be greater than 1.On the other hand suppose X is 0.2, then it will be pretty easy to input the formula to get valuable results.
