Karl wants to custom order 4 collars for his 4 unique cats A

Karl wants to custom order 4 collars for his 4 unique cats. A custom ordered collar is tailor fitted to a pet and comes in a choice of 9 different colors. How many selections of collars are possible if repetitions of colors are not allowed?

Each cat can have a colour in any of the 9 as repitition of colours is allowed.

Hence total no of ways possible = 9⁴ = 6561 ways