Computing operating income of the company

Question

Task:

                                 X       Y       Z
Sales                      $400   $200   $80
Variable expenses     128      52     34
Fixed expenses
Unavoidable               96      52      12
Avoidable                  116    104     54

1. compute the operating income of the company

2. compute the contribution margin and operating income of each department

3. should any department be eliminated, if so which ones and why?