Xia Co. currently buys a component part for $9 per unit. Xia believes that making the part would require $6.30 per unit of direct materials and $1.05 per unit of direct labor. Xia allocates overhead using a predetermined overhead rate of 240% of direct labor cost. Xia estimates an incremental overhead rate of $0.65 per unit to make the part.

1-a. What are the relevant costs for Xia to make or buy the part?

1-b. Should Xia make or buy the part?