Determine whether each of the following statements is true or false. For parts (d)-(g) provide a counterexample if the statement is false.
(a) The set Q+ is countable.
(b) The set R+ is countable.
(c) There is a one-to-one correspondence between the sets N and 2Z = {2k|k ∈ Z}.
(d) If A, B are countable sets, then A ⋃ B is countable.
(e) If A, B are uncountable sets, then A ⋂ B is uncountable.
(f) If A, B are countable sets, then A - B is countable.
(g) If A, B are uncountable sets, then A - B is uncountable.