With reference to the out-patient visits to a hospital, we consider the following events:

A: a patient is over 50 years of age;

B: a patient is under 25 years of age;

C: the condition of a patient upon arrival is considered to be serious;

D: a patient needs to stay at the hospital for at least one night.

We are given the following probabilities associated with the above events:

P(A) = 0.52, P(B) = 0.22, P(C) = 0.25, P(D) = 0.24, P(AC) = 0.17, P(AD) = 0.12, P(BC) = P(BD) = 0.06, P(CD) = 0.18, P(ACD) = 0.08.

Express in words what each of the following events represents and find the probability of occurrence for them:
A′B′, (A ∪ B)C, AC′ ∪ D, (A ∪ B)D′.