Consider the assembly line below. The three fabrication operations run in parallel, such that each batch of 20 units only needs to go through one of the three fabrication operations. After that, each batch needs to go through both assembly operations, which occur simultaneously (specifically, some components for each unit are assembled in the Assembly 1 area while others are assembled in the Assembly 2 area). The units are packaged and made ready for shipment in the final stage. What is the bottleneck time per batch of this operation?

Fabrication 18 min batch Assembly 1 8 min 2 batches Fabrication 18 min batch Packaging 4 min batch Assembly 2 2 min 2 batches Fabrication 18 min batch