A company assigns employee numbers according to the following scheme:

1. Each number must comprise three letters, followed by four numerals, followed by one letter.

2. There are no restrictions on the numerals.

3. There cannot be repetition among the first three letters; however, the final letter can be any letter, even if that letter is among the first three.

Which of the following expressions is equal to the number of possible employee numbers?

A company assigns employee numbers according to the following scheme:

1. Each number must comprise three letters, followed by five numerals.

2. The first numeral must be either '1' or '2'; there are no other restrictions on the numerals.

3. There cannot be repetition among the three letters.

4. To prevent confusion with the numerals '1' and '0', the letters 'I' and 'O' cannot appear.

Which of the following expressions is equal to the number of possible employee numbers?

A company assigns employee numbers according to the following scheme:

1. Each number must comprise two letters, followed by four numerals, followed by two letters.

2. There are no restrictions on the numerals.

3. There cannot be repetition between the first two letters.

4. There cannot be repetition between the last two letters.

5. A letter appearing as one of the first two letters can appear as one of the last two.

Which of the following expressions is equal to the number of possible employee numbers?