AST Electrical provides the following cost information related to its production of electronic circuit boards. PER UNIT: variable manufacturing cost: $40 fixed manufacturing cost: $30 variable selling and admin expenses: $8 fixed selling and admin expenses: $12 Desired ROI per unit: $15 Determine AST Electrical's markup percentage using variable-cost pricing. A.16.67%. B.50%. C.54.28%. D.118.75%.