. A construction firm is currently working on three different buildings. Let Ai denote the event that
the ith building is completed by the contract date. Use the operations of union, intersection, and
complementation to describe each of the following events in terms of A1, A2, and A3, draw a Venn
diagram, and shade the region corresponding to each one.
(a) At least one building is completed by the contract date.
(b) All buildings are completed by the contract date.
(c) Only the first building is completed by the contract date.
(d) Exactly one building is completed by the contract date.
(e) Either the first building or both of the other two buildings are completed by the contract date.