Q:

MVVM - Menu View with Preview View (Shared ViewModel) approach

I've just started my journey with MVVM and WPF and I need an advice to solve my problem or rather guide me towards right solution.
Link to image: https://s12.postimg.org/md0h6fv3x/Simple_App.png

Description (what I want to achieve):

View A is a menu (UserControl) with ListBox and DataContext: V.ObservableCollection

View B is a preview to selected item from View A ListBox

View A & B are loaded from MainWindow

What is simpliest and cleanest approach to achieve that?

I was thinking about sharing the same ViewModel with View A&B.
Create a SelectedItem property in ViewModel and then put it MainWindow's resources and bind datacontext to View A & B

Is it valid approach? Will that VM be updated properly in both views if it get changed?

Somehow bind View's A listbox SelectedItem to View B preview mode but don't know how.

A:

Use only one ViewModel.
Eg; Pseudo code : 
public class ViewModel : INotifyPropertyChanged
{
  public ObservableCollection<Employee>{get;}          

  /* provide change notification in ChosenItem */
  public Employee ChosenItem{get;set;}
}

Use this ViewModel as DataContext for both Views.

