Sandler Company manufactures electronic devices. The company is considering three cost drivers for measuring maintenance costs in the factory. The following cost functions have been estimated using each cost driver: Cost Driver Cost Function R2 1. X = number of parts Y = $20,000 + $5X R2 = 0.40 %3D 2. X = number of labor hours Y = $13,000 + $10X R2 = 0.95 %3D 3. X = number of machine hours Y = $15,000 + $7X R2 = 0.30 Which cost driver should be chosen? Select one: a. number of machine hours O b. none of the above O c. number of parts O d. number of labor hours