The cost to produce Part A was $27 per unit in 2019. During 2020, it has increased to $31 per unit. In 2020, Crane Company has offered to supply Part A for $26 per unit. For the make-or-buy decision, net relevant costs are $4 per unit. incremental costs are $4 per unit. incremental revenues are $5 per unit. differential costs are $5 per unit