Post Technologies Company has been purchasing carrying cases for its portable tablets at a delivered cost of $13.00 per unit. The company, which is currently operating below full capacity, charges factory overhead to production at the rate of 60% of direct labor cost. The total unit costs to produce comparable carrying cases are expected to be as follows: If Post Technologies Company manufactures the carrying cases, fixed factory overbead costs will not increase and variable factory overhead costs associated with the cases are expected to be 20% of the direct labor costs. a. Prepare a differential analysis report for the make-or-buy decision. Enter your final answer as a positive amount if it represents a net cost savings; enter a negative amount if it represents an increase in cost. b. On the basis of the data presented, would it be advisable to make the carrying cases or to continue buying them