10-38 Regression, choices between models. Tilbert Toys (TT) batches the popular Floppin 'Freddy Frog and Jumpin' Jill Junebug dolls. TT recently adopted activity-based costing. TT incurs setup costs for each batch of dolls it produces. TT uses the "machine configuration number" as the cost driver for the corresponding costs. TT just hired Bob Williams, an accountant. Bob believes that the "number of hours to set up machines" could be a better cost driver because the set up time for each product is different. Bob collected the following data: