Answer: 
$1,576,000
Explanation:
The computation of the combined total net income is shown below:
<u>Particulars     Normal volume  Additional volume  Combined total
</u>
Sales              $6,000,000         $480,000               $6,480,000
                                                 (40,000 × $12) 
Less: Costs and expenses    
Direct material $800,000            $80,000               $880,000
                                            ($800,000  ÷ 400,000 × 40,000)
Direct labour    $1,600,000         $160,000             $1,760,000
                                          ($1,600,000 ÷ 400,000 × 40,000) 
Overhead        $400,000          $64,000                $464,000
                                                 ($400,000 × 16%) 
Selling expenses $600,000     $0                         $600,000
Administrative 
expense           $1,028,000   $172,000                $1,200,000
Total costs 
and expenses $4,428,000    $476,000             $4,904,000
Incremental 
income 
(loss) from 
new busines   $1,572,000   $4,000               $1,576,000
We assume reduced price of $12 per unit instead of $13 per unit