Folder Share Permission Setup

HI,

  How do i give permission (NTFS) for following users ( user a, userb, and userc) to following folders?

create area1-read group and add usera 

      \\RootShare\Sales\area1  --- Usera read access  ( userb & userc no access)  add area1-read group 

      \\RootShare\Sales\area2----- Userb read access  ( usera & userc no access)

     \\RootShare\Sales\area3------ Userc read access  ( userb & usera no access)

area1 got only one group area1-read .

usera cannot access this folder? if i add domain users he can?