A building may fail by excessive settlement of foundation or by collapse of the superstructure. Over the life of the building, the probability of excessive settlement of the foundation is estimated to be 0.10, whereas the probability of collapse of the superstructure is 0.05. Also if there is excessive settlement of the foundation, the probability of superstructure collapse will be increased to 0.20. What is the probability that the building failure will occur over its life? What is the probability that only one of the two failure modes will occur over the life of the building? If building failure should occur during its life, what is the probability that both failure modes will occur?