A community has three major sources of power supply: electricity, gas and oil. Let E, G and O denote events of shortages of each of these power sources, respectively. Their probabilities are estimated to be 0.15, 0.10 and 0.20 respectively. Furthermore, assume that if there is a shortage in the oil supply, the probability of an electrical power shortage will be doubled, that is twice the probability of P(E). The shortage of gas may be assumed to be independent of shortages of oil and electricity.
a. What is the probability that there will be a shortage of all three major sources of power supply?
b. If there is a shortage of electricity, what is the probability that gas and oil also will be short?