A farmer has a grain bin with 4,000 cubic feet of barley in it. He uses 800 cubic feet to feed his herd of cows. The next day, he buys 800 cubic feet of barley and puts it into the grain bin. How many cubic feet of barley are in the grain bin now?
A) 2,400
B) 4,000
C) 4,800
D) 5,600