
    
<p>How many different solutions can you find to this problem?</p>
<p>Arrange 25 officers, each having one of five different ranks a,
b, c, d and e, and belonging to one of five different regiments p,
q, r, s and t, in a square formation 5 by 5, so that each row and
each file contains just one officer of each rank and just one from
each regiment.</p>