How far should the bottom of the camera target be from the ground when adjusting the cameras for a Cisco TelePresence System 1300?

How far should the bottom of the camera target be from the ground when adjusting the cameras for
a Cisco TelePresence System 1300?

A.
22 inches (56 cm)

B.
32 inches (81 cm)

C.
42 inches (107 cm)

D.
48 inches (122 cm)