Focus also on the D requirement

15 Arthur's Plumbing reported the following: Revenues Variable manufacturing costs Variable nonmanufacturing costs Fixed manufacturing costs Fixed nonmanufacturing costs $4,500 $ 900 $ 810 $ 630 $ 545 Required: a. Compute contribution margin. b. Compute contribution margin percentage. c. Compute gross margin. d. Compute gross margin percentage. e. Compute operating income