Colony Shop is stocking heavy coats for next winter. Colony pays $50 for a coat and sells it for $110. At the end of the winter season, Colony offers the coats at $55 each. The demand for coats during the winter season is more than 20 but less than or equal to 30, all with equal probabilities. Because the winter season is short, the unit holding cost is negligible. Also, Colony’s manager does not believe that any penalty would result from coat shortages. Using continuous approximation, determine the optimal order quantity that will maximize the revenue for Colony Shop.