Sienna Manufacturing uses a two-step process to make a metal part. The first step involves cutting with a machine that requires a 40-minute setup time before the production of each batch. The cutting takes 30 minutes per part. The second step is polishing the parts from cutting. The polishing takes 40 minutes per part, and the polishing machine requires no setup. Assume demand is unlimited. What is the ideal batch size of the parts?
a. 10
b. 8
c. 4
d. 2