As per my understanding we need Time and Motion study for a particular process, which would provide us with AHT (Average Handling Time) for a particular transaction.

If we have sub-processes than we need to have seprate T&M study with seprate AHT. Then we need average voulme for all sub-processes which would give us avg. volume for entire process (by adding vag. volume of all sub-processes).

So with all these data we can easily calculate the FT required and total time need for deliverables.