To use the queuing theory model to assess waiting lines, which of the following conditions need NOT be met: a. Units must arrive randomly for service. b. The time a unit waits cannot be influenced by when the previous unit arrived or exited the system. c. The number of units waiting has no influence on when a unit arrives for services. d. The time it takes to service a unit (e.g. provide a service) is predetermined and fixed (e.g. 5 minutes per patient)