Determine whether the following problem involves a permutation or combination. (It is not necessary to solve the problem)
How many different 7-letter passwords can be formed from the letters O,P,Q,R,S,T, and U if no repetition of letters is allowed?
How many different 7-letter passwords can be formed from the letters O,P,Q,R,S,T, and U if no repetition of letters is allowed?