Exercises
[031] Show that if \(| A_ 1|\le | A_ 2| \) and \(| B_ 1|\le | B_ 2| \) then \(| A_ 1\times {B_ 1}|\le | A_ 2\times {B_ 2}|\).
[031] Show that if \(| A_ 1|\le | A_ 2| \) and \(| B_ 1|\le | B_ 2| \) then \(| A_ 1\times {B_ 1}|\le | A_ 2\times {B_ 2}|\).