Which IP address and subnet mask combination would most efficiently accomplish this?

You are Cisco Express Foundation Design Specialist in a company. Your company two primary
divisions: Sales and Financial. The Sales division is on network 140.10.64.0/21. The Financial
division is on network 140.10.72.0/21. You want to summarize both networks into one routing
statement. Which IP address and subnet mask combination would most efficiently accomplish
this?

A.
140.10.64.0/21

B.
140.10.64.0/22