Beta Company sells several products. Information of average revenue and costs is as follows:

              Selling price per unit                           $23

              Variable costs per unit:

                     Direct material                             $5

                     Direct manufacturing labour        $1.96

                     Manufacturing overhead             $0.55

                     Selling costs                                $4

              Annual fixed costs                              $91278

The company sells 10365 units during the period. If the direct labour and direct material per unit cost increases by $1 each, the total contribution margin for the period will decrease by $________.