To Huawei Probe&Assistant software side, about the dropped calls formula definition, which of the following is correct?

To Huawei Probe&Assistant software side, about the dropped calls formula definition, which of the following is correct?
A . Call Drop Rate = eRAB AbnormRel/eRAB Setup Success *100%
B . Call Drop Rate = eRAB AbnormRel/RRC Connection Setup Success *100%
C . Call Drop Rate = eRAB AbnormRel/eRAB Release Total *100%
D . Call Drop Rate = eRAB AbnormRel/eRAB NormRel *100%

Answer: A