Metal frames for kick scooters are manufactured in two steps: Stamping and assembly. Each frame is made up of three pieces: one unit of part A and two units of part B. The parts are fabricated by a single stamping machine that requires a set up time of 60 minutes switching between two part types. Once the machine is set up, the activity time for parts, regardless of type, is 0.4 minutes each piece. Currently, the stamping machine rotates its production between one batch of 100 part As and 200 part Bs. At assembly, parts are assembled manually to form the finished products. The three parts and a number of small purchased components are required for each unit of final product. Each product requires 60 minutes of labor time to assemble. There are 30 workers in assembly. There is sufficient demand to sell every scooter the system can make. What batch size for the stamping machine would minimize inventory while allowing assembly to operate at its maximum flow rate?