Exercise 22-8 Rensing Groomers is in the dog-grooming business. Its operating costs are described by the following formulas: Grooming supplies (variable) Direct labor (variable) Overhead (mixed) y = y = y = $0+$4x $0 + $13x $10,200 + 1x Milo, the owner, has determined that direct labor is the cost driver for all three categories of costs