Identify the equation that determines the cost of units in beginning work-in-process under the first-in, first-out costing method. O a. Cost of Units in Beginning Work-in-process = Unit Cost x Units Completed O b. Cost of Units in Beginning Work-in-process = Unit Cost Equivalent Units Started and complete O c. Cost of Units in Beginning Work-in-Process = (Unit Cost x Equivalent Units to Complete) + Prior-Period Costs Od. Cost of Units in Beginning Work-in-process = (Unit Cost Units Started and completed) + Prior-Period Costs