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[25 points] A small retailer of snorkeling equipment must decide how many snorkeling masks to order for this summer season. The selling price for these masks is $25, while the cost to the retailer is $20. The retailer is very concerned about loss of good will, so she does not allow any unsatisfied demand. In order to achieve this, she buys additional masks from her competitors at their retail price of $32 when she is out-of-stock, and sells these masks at regular price of $25 to her customers. Masks left over at the end of the short selling season are sold at a special discount price of $14 per mask. The retailer knows that all leftover masks will be sold under the discount price. (a) Calculate the cost of over-ordering and the cost of under-ordering. (b) Assume that the demand for snorkels follows a uniform distribution between 400 and 800 units. In this case, how many snorkels should the owner order in advance