I want accurate answer with proper explanation please I'll upvote show all your work no handwriting

Security expert McCue suggests another way to make the codes more secure. Using a keypad shown here, users type in 4 letters as CLEAR the secret code. Letters will not repeat in the code. McCue says this will make the system much more secure. Agent Miller disagrees, saying that since 4 letters are chosen, the number of possible codes is still 4x3x2x1 = 24. Who do you agree with? I agree with Agent McCue or I agree with Agent Miller? Explain your thinking.

Agent Miller is wrong because there are not 24 ways to crack the combination because there are 8 buttons, not 4. It should be 8 x 7 5 x 6. There has to be a proper sequence. There are not 4 options there are 8 options. Also, there is no repetition, making it a probability question and not a combination. The order matters.

How many different codes could we make if users needed to use all 8 letters and the code is 8 letters long? Assume that no letter will repeat. Enter an expression that helps find the answer.

How many different codes could we make if users needed to use all 8 letters - and the letters COULD repeat? Enter an expression which helps find the answer.