A treasure chest contains 81 figurines. Each figurine comes in one of three different colors (red, yellow, and blue), one of three different shapes (circle, triangle, and square), and one of three different sizes (big, medium, and small). Each figurine also has its edges covered in a casing of one of three different metals (gold, silver, and bronze). If you pull three figurines out at random (the order in which you pull them out is irrelevant), what's the probability that no two of the figurines you pull out will be a.) of the same color, shape, or size, or b.) encased in the same metal?
