Drawing of three squares lined up in a row. The square on the left is titled "I" and contains 30 purple bubbles. The square in the center is titled "II" and contains 15 purple bubbles and 15 blue bubbles. The bubbles are mixed unevenly throughout the square. The square on the right is titled "III" and contains 15 purple bubbles and 15 blue bubbles. The bubbles in this square have a pattern, in which every other bubble is the same color.