Which conference resource does the sixth conference use?

Refer to the exhibit.

You have six IP phones configured to use MRGL_CFB. Each phone is making a conference call.
Which conference resource does the sixth conference use?

A.
HW_CFB_1

B.
HW_CFB_2

C.
SW_CFB_1

D.
SW_CFB_2

E.
SW_CFB_3