First select 1 man and a woman
This can be done in 13c113c1 ways i.e 132 ways.
Then for every of this selections select the second pair out of the 12 remaining pairs.
This can be done in 12c112c1 ways i.e 122 ways. and so on....
Therefore total ways= (132)(122)..........(12)= (13!)2=38775788043632640000
It's quite a large number--- isn't it?
Rate please.