Question 1139436
.
<pre>

In all, Carl can use 26 + 10 = 36 symbols.


Without repeating, there are  36*35*34*33 = 1413720 different possible codes.



Any of 36 symbols in the very first leftmost position;

then any of 35 remaining symbols in the 2-nd position;


    . . .  and  so  on  . . . 
</pre>