this sort of give/learn/take averaged over multiple employees could redefine how much can be done in a week, or what the average rate per hour is, but in the end the time would be spent more efficiently. I believe that having a set number of hours will grow the workload to meet those hours, and that's inefficient in most cases. No studies to back this up, but I've worked in a lot of places, and the percentage of people that are actually trying to get done as much as they can [in a working day] is very low.