Answer :

Step-by-step explanation:

nnnllll

the first number has 10 options (0 .. 9).

the second number has 9 options, as repeats are not allowed.

for the same reasons the third number has then only 8 options.

then, the first letter has 26 options (a .. z).

the second letter has 25 options. again, because repeats are not allowed.

the third letter has then 24 options.

the fourth letter only 23 options.

so, altogether, for the whole password, we have

10×9×8×26×25×24×23 possible passwords.

that are

258,336,000

possible passwords