Question 248211
for the first character ask your self
how many letters are there?
second character
how many letters are there?
how many letters can there be in the second position?
so it would be the first character amount times the second character amount.
how many digits are there?
that many times the total last amount.
can digits be repeated? then the last total time that number and 
The final character same number of diigtis time the last product

so the main questions to ask in place are
 how many characters (letters and digits) of this type are there? 
and how many are allowed?
multiply that by the last product.