A utility company offers a lifeline rate to any household whose electricity usage falls below 240 kWh during a particular month. Let A denote the event that a randomly selected household in a certain community does not exceed the lifeline usage during January, and let B be the analogous event for the month of July (A and B refer to the same household). Suppose , and . Compute the following:

a) . . So = .8 + .7 - .9 = .6

b) The probability that the lifeline usage amount is exceeded in exactly one of the two months. Describe this event in terms of A and B. I believe this would be an XOR relationship between A and B, so that would be

Please let me know if these calculations and set relationships are accurate.