Answer:
$7.1 cost per unit.
Step-by-step explanation:
Incremental cost are the cost incurred when settling for an alternative between two options.
In calculating incremental cost , variable cost are the relevant cost as fixed costs will always be incurred regardless of the options settled for
Variable cost of production
Direct material - $9.10
Direct labor - $13.10
Variable overhead - $2.10
$24.3
Cost of buying from an outside supply is $31.40
Incremental cost of buying = $7.1