I mill 9 + 4 = 2. I mill 3 - 4 = X. I PBA-withdraw a 4 crop. I PBA-withdraw an 8 crop. I mill 4 * 8 = X. I PBA-withdraw a 4 crop. I PBA-withdraw a 4 crop. I PBA-withdraw a 7 crop. I PBA-withdraw a 7 crop. I mill 4 / 7 = X. I mill 4 / 7 = X.
I PBA-deposit an X crop. I PBA-deposit an X crop. -woggle
