Riggs Company purchases sails and produces sailboats. It currently produces 1, 230 sailboats per year, operating at normal capacity, which is about 80 % of full capacity. Riggs purchases sails at $ 275 each, but the company is considering using the excess capacity to manufacture the sails instead. The manufacturing cost per sail would be $ 94.33 for direct materials, $ 80.41 for direct labor, and $ 90 for overhead. The $ 90 overhead includes $ 78, 400 of annual fixed overhead that is allocated using normal capacity. The president of Riggs has come to you for advice. "It would cost me $ 264.74 to make the sails, " she says, "but only $ 275 to buy them. Should I continue buying them, or have I missed something?" Prepare a per unit analysis of the differential costs. (Round answers to 2 decimal places, e.g. 15.25. Enter negative amounts using either a negative sign preceding the number e.g. -45 or parentheses e.g. (45).) Should Riggs make or buy the sails