Both Bob and Charles have complete and transitive preferences. Diana's preference is as follows: to compare two bundles X and Y, Diana rst asks her two best friends, Bob and Charles. If both Bob and Charles strictly prefer X to Y, then Diana will also strictly prefer X to Y; if both Bob and Charles strictly prefer Y to X, then Diana will also strictly prefer Y to X; if both Bob and Charles are indi erent between X and Y, and Diana will also be indi erent between X and Y. Discuss whether Diana's preference violates any of the four assumptions on preferences (monotonicity, convexity, completeness, and transitivity)