Suppose that a computer user chooses six random characters (either letters or digits)

for a website password. (For example, I just chose ZDQMF2.) Characters can be used more than once (as with ZDZMF2) and no distinction is made between upper case and lower case letters. Suppose that a password attacker tries to enter your account by trying passwords with six randomly chosen characters but gets only three tries before the website locks the account for 24 hours. Because the attack program uses randomly selected characters, it may try the same six characters more than once. What is the probability that the three tries will be enough to access your account?