Sunshade produces a special canvas top for its high quality aluminum gazebo. The costs to produce the 900 units needed each year are as follows: Treated canvas fabric $144,000 Aluminum poles 36,000 Aluminum frame fittings 9,000 Direct labor 72,000 Variable manufacturing overhead 22,500 Fixed manufacturing overhead 58,500 $342,000 Total costs Coolaroo has offered to make the needed canvas tops of comparable quality for $293 each, FOB shipping point. Sunshade would pay for shipping at a cost of $50 per unit. Sunshade's accountant has estimated that 20% of the fixed overhead can be avoided if the tops are purchased. Sunshade should: Select one: a. Buy the part, thereby saving $3 per unit. b. Buy the part, thereby saving $10 per unit. c. Make the part, thereby saving $15 per unit. d. Buy the part, thereby saving $5 per unit.