Answer and Explanation:
The preparation of the incremental analysis is presented below
Particulars        Make      Buy net Income Increase or (decrease)
Direct material  $120,000       -     $120,000
             [$4 × 30,000]
Direct labor     $150,000         -  $150,000
                [$5 × 30,000]
variable manufacturing $105,000 Â Â Â - Â Â Â Â $105,0000
              [$150,000 × 70% ]
Fixed manufacturing $45,000 Â $45,000 Â Â Â Â -
Purchase price      -      373,560    -$373,560
                             [30,000 × $12.95 ]
Total annual cost $420,000 Â Â Â $433,500 Â Â -$13,500
There is a decrement of $13,500 so it should be make decision rather buying decision