[PCI DSS 1.x] 9.4 Use a visitor log to maintain a physical audit trail of visitor activity. Retain this log for a

9.4.a Verify that a visitor log is in use to record physical access to the facility as well as for computer rooms and data centers where cardholder data is stored or transmitted
9.4.b Verify that the log contains the visitor’s name, the firm represented, and the employee authorizing physical access, and is retained for at least three months

does this only apply to computer room? or the entire office?