Answer:
The book case should be processed further
Explanation:
                  Sell Option  Process Further  Increase/Decrease
Sales per unit          $58.51      $70.45            $11.94
Cost per unit:
Variable               $37.56      $45.97            ($8.41)
Fixed                  $9.67       $9.67             $0
Total cost              $47.23      $55.64            ($8.41)
Net income per unit     $11.28      $14.81             $3.53
Conclusion: The book case should be processed further as its Net Income per unit is higher than if the Pine street should sell.