A process comprises following two steps: First, step A is carried out by machine A, which is followed by step B, which is carried out at machine B. Step A has set- up time of 45 minutes and run time of 1 minute, whereas Step B has no set up time but run time of 1.5 minutes. Currently demand is 30 jobs per hour and batch size is 150 jobs. What batch size minimizes the flow time without changing process capacity (from its current level)? 120 90 30 60