Number of defective cell phone produced = 1000.
Defective phones cost $30 each.
Cost of defective phones =30x1000=30,000.
Cost of producing 1000 cell phones = 60x1000=$60,000.
Cost of rework= 80x1000=80,000.
Rework phone sale value =120x1000=120,000.
Incremental net income = 120,000-80,000-30,000= $10,000.
The incremental net income from reworking the phones is $10,000.