When Cisco IOS IPS signatures are being tuned, how is the Target Value Rating assigned?

When Cisco IOS IPS signatures are being tuned, how is the Target Value Rating assigned?

A.
It is calculated from the Event Risk Rating.

B.
It is calculated from a combination of the Attack Severity Rating and Signature Fidelity Rating

C.
It is manually set by the administrator.

D.
It is set based upon SEAP functions.