Hydrology question: an urban drainage canal reaches flood stage each summer with relative frequency of 0.10; power failures in industries along the canal occur with a probability of 0.20; experience shows that when there is a flood for what ever reason the chances of power failure raised to 0.40. what is the probability of no flood in the area? what is the probability that power failure given that a flood occurs? what is the probability that a flood occurs but no power failure? what is the joint probability of no flood and no power failure in the area? what is the probability of a flood or power failure in the area?