The quantity of pet rocks fell sharply last month, while the price remained the same. Each of five people suggests an explanation: Ned: Demand decreases, but supply decreased at the same time. Robert: Supply decreases, but demand is perfectly elastic. Stannis: Demand increases, but supply increased at the same time. Robb: Demand decreases, but supply is perfectly inelastic. Drogo: Demand decreases, but supply is perfectly elastic. Whose explanations are correct