How many 4 letter code can be formed using the first 9 letters of the English alphabets, if no letter can be repeated?

Question: How many 4 letter code can be formed using the first 9 letters of the English alphabets, if no letter can be repeated?

Solution:
By fundamental principle, it is (9 × 8 × 7 × 6) ways
= 3024 ways

Alternative:
⁹P₄ = 9!/(9 - 4)!
= 9!/5!
= (9 × 8 × 7 × 6 × 5!)/5!
= 3024 ways