Answer:
a) result from costs in the beginning inventory being added in with current period costs.
Step-by-step explanation:
Because the FIFO means First In First Out
the beginning inventory AKA cost from prior period will be include to determinate the cost of the units that made first in. Then the remaining cost added to finish this units will be assing to calculate the cost of units under FIFO
example
100 units BI WIP $5,000
cost added to finish this units $10,000
Total cost $15,000
units cost $15,000/100 = $150
If there are more units finsihed during the period, they may have a diferent units cost.