Answer:
A. $2,900.
Explanation:
Beginning balance of Office Supplies account = $600
Ending balance of Office Supplies account = $400
Supplies expense for the year = $3,100
Ending balance of Office Supplies account = Beginning balance of Office Supplies account + Purchases for the year - Supplies expense for the year
Purchases for the year = Ending balance of Office Supplies account + Supplies expense for the year - Beginning balance of Office Supplies account
Purchases for the year = 400 + 3100 - 600
Purchases for the year = 2,900