um well i dont really know.. but err
u can only hav 1 letter or number in each spot right. ABC 123
therefore wouldnt that just mean 26P1 x 26P1 x 26P1 x 10P1 x 10P1 x 10P1?
thats the same as 26^3 x 10^3 i know but, i cant think of any other explanation sorry.
o btw..permutations r...