Junior Company currently buys 30,000 units of a part used to manufacture its product at $40 per unit. Junior has some additional space and could produce the units for the following per-unit costs (based on 30,000 units): Direct materials $16 Direct labor $12 Variable overhead $12 Fixed overhead $10 Total $50 If the units are purchased from the supplier, $200,000 of fixed costs will continue to be incurred. In addition, the plant can be rented out for $20,000 per year if the parts are purchased externally. Which alternative (internal production or external purchase) is more cost effective? And by how much (using relevant amounts only)?