Question 188
In how many ways can we enter numbers from the set $\{1,2,3,4\}$ into a $4 \times 4$ array so that all of the following conditions hold?
(a) Each row contains all four numbers.
(b) Each column contains all four numbers.
(c) Each "quadrant" contains all four numbers. (The quadrants are the four corner $2 \times 2$ squares.)
(a) Each row contains all four numbers.
(b) Each column contains all four numbers.
(c) Each "quadrant" contains all four numbers. (The quadrants are the four corner $2 \times 2$ squares.)