Kick Scooters Metal Frames for Kick Scooters Are Manufactured in Two Steps

Kick Scooters
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 90 minutes switching between two part types. Once the machine is set up, the activity time for parts, regardless of type, is 30 seconds each piece. Currently, the stamping machine rotates its production between one batch of 120 part A's and 240 part B's. Completed parts move only when the entire batch is produced.
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 30 minutes of labor time to assemble. There are 12 workers in assembly. There is sufficient demand to sell every scooter the system can make
-Which batch size for the stamping machine would minimize inventory without decreasing the current flow rate? Circle the answer below that is closest to the correct answer.

A) 60 sets
B) 120 sets
C) 180 sets
D) 240 sets