A building is designed to resist loading from earthquakes. The capacity (in terms of force factor) is assumed to follow a lognormal distribution with a median of 6.5 and a standard deviation of 1.5. The maximum possible earthquake will have an quivalent force factor of 5.5.
There are 5 buildings in a complex. Find the probability that at least 4 out of 5 will survive 100 years without damage.