Consider the hospital emergency room data given below. let a denote the event that a visit is to hospital 4, and let b denote the event that a visit results in lwbs (at any hospital). use the addition rules to calculate the following probabilities. (a) p(a union b) (b) p(a union b') (c) p(a' union b') determine the following probabilities. (d) p (a|b) (e) p(a'|b) (f) p(a|b') (g) p(b|a) determine the following probabilities. (a) p(a intersection b) (b) use the total probability rule to determine p(a) again, let a denote the event that a visit is to hospital 4, and let b denote the event that a visit results in lwbs (at any hospital). are these events independent? explain.