An investment adviser that typically places about 900 trades per month for its clients receives a notice from its executing broker that the cost per trade will drop to a flat $8.00 from the current $12.00 if 1,000 trades per month are placed. The investment adviser wishes to take advantage of the discount. To do this, the investment adviser should effect the extra 100 trades per month:
A. across its customer accounts in proportion to the size of each account
B. divided equally across all customer accounts
C. across its customer accounts in proportion to trading activity in each account
D. in the adviser's proprietary accounts