Use cartesian product and other set operations to describe the following sets. a) the set of all passwords containing at least 8 and at most 10 symbols and consisting of upperand lowercase letters b) the set of all passwords containing at least 8 and at most 10 symbols, consisting of upper- and lowercase letters and digits and beginning with a letters c) the set of all passwords as described in b) which also contain at least one digit d) (*) the set of all passwords as described in question c) which contain at most three digits