A four-step process is used to make a product. The first resource takes 8 minutes per unit, the second takes 7 minutes per unit, the third takes 2 minutes per unit, and the fourth takes 10 minutes per unit. 20% of all units have to be reworked. For that, they have to revisit the third and fourth resources. Each resource is staffed by one worker. Rework takes the same processing times as the first pass and always fixes the problem. What is the capacity of the process in units per minute?