A set is countable if it is finite or has the same cardinality as N. A set that is not countable is called uncountable. For example, R is known to be uncountable. Determine whether each of the following sets is finite, countably infinite, or uncountable. For those that are countably infinite, find a bijection between N and that set.
(a) odd negative integers.
(b) integers whose square is less than 100,000,000.
(c) real numbers between 5 and 50.
(d) integers of the form 3k + 2 for some k ∈ Z.