"Firms Need to Use the Capacity of the Equipment or Division

Essay

"Firms need to use the capacity of the equipment or division that is the 'bottleneck' of the manufacturing process as the denominator volume in setting the fixed overhead allocation rate.In cases where there is more than one 'bottleneck,' the denominator should be the smallest capacity among the bottleneck production processes."
Required: (a)What type of variance is related to this "denominator?" Explain.
(b)Why should a firm choose the smallest capacity "bottleneck" as the denominator in a manufacturing process?