7 (6 points) Porpoise Co. makes oil filters that cost an average of $11.20/unit at the 25,000-unit level of activity and $10.85 at the 40,000 unit level of activity. The relevant range of activity levels is 15,000-75,000 units. (a) Using the high/low method, predict the variable cost per unit. (b) Estimate the fixed costs for the activity period. (c) What would Porpoise's contribution margin be if the company produced 35,000 units in a period and sold them all for $30 each. F2 80 F3 F4 F5 F8 F7 F 2 3 $ 4 % 5 E R T U S D H V B N E9 9 K M