Give examples of languages L1 and L2 over {a, b} that satisfy
the descriptions below:
(a) L1 is regular, L2 is nonregular, and L1 U L2 is regular;
(b) L1 is regular, L2 is nonregular, and L1 U L2 is
nonregular;
(c) L1 is regular, L2 is nonregular, and L1 n L2 is regular;
(d) L1 is nonregular, L2 is nonregular, and L1 U L2 is
regular.
(e) L1 is nonregular, L2 is nonregular, and L1 n L2 is
regular.