Please show detailed workings

The 20X6 data that follow pertain to Rays, a manufacturer of swimming goggles. Rays had no beginning inventories in January 20X6. a) Calculate the following for Rays i) The total cost per unit ii) The value of ending inventories using marginal costing iii) The value of ending inventories using total costing b) Prepare a variable costing (contribution margin) income statement for Rays for the year ended December 31, 20X6. c) Rays marketing vice president believes a new sides promotion that costs $150,000 would increase sales to 200,000 goggles. Should the company go ahead with the promotion? Give your reason