premise: Each of seven toy dinosaurs—an iguanadon, a lambeosaur, a plateosaur, a stegosaur, a tyrannosaur, an ultrasaur, and a velociraptor—is completely colored either green, mauve, red, or yellow. A display is to consist entirely of exactly five of these toys. The display must meet the following specifications: Exactly two mauve toys are included. The stegosaur is red and is included. The iguanadon is included only if it is green. The plateosaur is included only if it is yellow. The velociraptor is included only if the ultrasaur is not. If both the lambeosaur and the ultrasaur are included, at least one of them is not mauve. If both the iguanadon and the ultrasaur are included in the display, then the display must contain which one of the following?
hypothesis: a mauve tyrannosaur