I am trying to do the following and need advice on how to do it:

1. I'm assigning sub tasks and even sub-sub tasks under various tasks in a project template. In all there are around 20 or so sub tasks.  I can go to each of the 20 sub tasks and assign it individually, but that is tedious. Is there a way to assign

(a) all of the sub tasks under a task to one particular person at one shot?

(b) the entire project to one particular person at one shot?

2. I have assigned durations for each of the sub tasks under a task. The duration of the task should ideally be a sum of the durations of the  sub-tasks, but I see no way to set that. Is there a way I can do that? 

Similarly the duration of the whole project should be a sum of the durations of each of the tasks in the project. Is there a way to set that?

Thanks
Satya NHM