Railways - Engineering

Q1:

For calculating the length of curve lead (C.L.), the correct formula is

A C.L. = G. cot α/2

B
C.L. = 2IG

C C.L. = 2 GN

D all the above.

ANS:D - all the above.

Shouldn't the answer be c) C.L. = 2 GN?

Anyone, please clarify.