A conveyor belt sushi restaurant lets you choose what you want to eat from variously-coloured plates that go by. You pay based on the colours of the plates. After dinner, 1 green plate, 4 yellow plates, and 2 blue plates. Use the Fundamental Counting Principle to count how many ways that they can make the two stacks of plates.

The Fundamental Counting Principle states that if we have m ways of doing one thing, and n ways of doing another thing, then there are m*n ways of doing both things together.

In this case, we have 1 green plate, 4 yellow plates, and 2 blue plates. Let's first consider the number of ways that we can arrange the 1 green plate and 4 yellow plates:

- For the position of the green plate, we have 2 choices: it can be either in the first stack or in the second stack.
- For the position of the 4 yellow plates, since they are identical, it doesn't matter which order they are in. This means there is only 1 way to arrange them.

Therefore, by the Fundamental Counting Principle, the number of ways to arrange the green and yellow plates is 2 * 1 = 2.

Now, let's consider the number of ways to arrange the blue plates:

- For the position of the first blue plate, we have 3 choices: it can be in either the first stack, second stack, or between the two stacks.
- For the position of the second blue plate, we also have 3 choices.

Therefore, there are a total of 3 * 3 = 9 ways to arrange the blue plates.

Finally, to find the total number of ways to make the two stacks of plates, we multiply the number of ways to arrange the green and yellow plates (2) by the number of ways to arrange the blue plates (9):

2 * 9 = 18

So, there are 18 ways to make the two stacks of plates with 1 green plate, 4 yellow plates, and 2 blue plates.

which two stacks?