Consider telephone calls made to a company's complaint line. Let A be the event that the call is answered within 10 seconds. Let B be the event that the call is answered by one of the company's experienced telephone operators. Let C be the event that the call lasts less than 5 minutes. Let D be the event that the complaint is handled successfully by the telephone operator. Describe the following events.
(a) B ∩ Cʹ
(b) (A ∪ Bʹ) ∩ D
(c) Aʹ ∩ Cʹ ∩ Dʹ
(d) (A ∩ C) ∪ (B ∩ D)