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

Your company has two primary divisions: Products and Services. The Products division is on network 150.10.64.0/21. The Services division is on network 150.10.72.0/21. You want to summarize both networks into one routing statement. Which IP address and subnet mask combination would most efficiently accomplish this?

A.
150.10.64.0/22

B.
150.10.64.0/20

C.
150.10.0.0./16

D.
150.10.64.0/21