We naturally order the numbers in \(A_{m}=\\{1,2, \ldots, m\\}\) with "less than
or equal to," which is a partial ordering. We define an ordering, \(\preceq\) on
the elements of \(A_{m} \times A_{n}\) by
$$
(a, b) \preceq\left(a^{\prime}, b^{\prime}\right) \Leftrightarrow a \leq
a^{\prime} \text { and } b \leq b^{\prime}
$$
(a) Prove that \(\preceq\) is a partial ordering on \(A_{m} \times A_{n}\).
(b) Draw the ordering diagrams for \(\preceq\) on \(A_{2} \times A_{2}, A_{2}
\times A_{3},\) and \(A_{3} \times A_{3}\).
(c) In general, how does one determine the least upper bound and greatest
lower bound of two elements of \(A_{m} \times A_{n},(a, b)\) and
\(\left(a^{\prime}, b^{\prime}\right) ?\)
(d) Are there least and/or greatest elements in \(A_{m} \times A_{n} ?\)