If we're just choosing from how many colors are there? There's one, two, three, four, five, six colors. And we're going to pick four of them. How many four-color codes can be made if the colors cannot be repeated? And since these are codes, we're going to assume that blue, red, yellow, and green is different than green, red, yellow, and blue. We're going to assume that these are not the same code. Even though we've picked the same four colors, we're going to assume that these are two different codes.