A camper lights an oil later at 12 noon and lets it burn continuously. Once the lantern is lit, the lantern burns oil at a constant rate each hour. At 2pm, the amount of oil left in the lantern is 63 ounces. At 5pm, the amount of oil left in lantern is 61 1/2 ounces. Based on the average rate of oil burning per hour, how much oil, was in the latern at 12 noon?