4. The FIFO method is used by Woolley Inc. in its process costing system. The information below pertains to the activities of the company's first production department for the previous month. WIP, beginning: Units in process 100 In terms of materials, the stage of completion is In terms of conversion, the stage of completion is. 50% 90% Costs in the beginning inventory: Materials cost...... $260 Conversion cost..... $3,366 Units started into production during the month. 20,000 Units completed and transferred out. 19,800 Costs added to production during the month: Materials cost. $99,650 $745,329 Conversion cost. WIP, ending: Units in process. In terms of materials, the stage of completion is In terms of conversion, the stage of completion is. 300 60% 20% a. Using the FIFO method of process costing, construct a production cost worksheet with supporting schedules. (15%) b. "In my process-costing system, there's no need for me to get excited about the option between the weighted-average and FIFO approaches. My materials suppliers and I have long-term, fixed-price contracts." Do you agree with this plant supervisor's statement? Please explain! (5%)