how many different ways can 4 different brands of toothpaste be displayed?

On a shelf, looking from left to right:

   there are 4 choices for the first brand

      there are 3 choices for the second brand

         there are 2 choices for the third brand

            and there is only 1 choice for the last brand.

To find the total number of choices, multiply these numbers together:  4 x 3 x 2 x 1  =          <---  answer