2. A bread-making factory has the production process shown in the figure below. There are five operations in sequence. The product only needs to go through one of the parallel machines in each case where parallel machines exist. What is the bottleneck time per batch of this process? Proof 60 min./batch Bake Mix 50 min/batch Pack 40 min./batch 60 min./batch Proof 60 min./batch Cut 35 min./batch Mix Bake Pack 40 min./batch 50 min/batch Proof 60 min./batch 60 min./batch