Process Costing:

2. The following data are available for materials costs at ZETA Company. Equivalent units transferred out20000 Equivalent units produced this period using FIFO33000 Equivalent units in beginning inventory7000 Materials costs in beginning work in process inventory$20000 Current period costs for materials$80,000

Which method has the lowest unit cost? A. Weighted average B. Fifo C. Both methods give the same unit cost D. Unit costs do not depend on the method used

I know the answer is B but don't understand why or how to calculate. Please show all work and explain the steps