Question 4: Total: 25 marks Below are the processing costs of Hartley Products observed over the last 12 months: Month Processing Cost 1 2 3 4 5 Units Produced 8,500 14,000 16,000 5,500 9,000 8,500 4,700 7,000 12,500 6,000 7,200 6,200 6 $51,000 57,000 60,000 38,000 47,000 52,000 34,000 41,000 53,000 41,000 42,300 40,600 7 8 9 10 11 12 a. Use the high low method to determine the variable cost per unit and fixed cost per month. Express your results in the form of a linear equation y = a + bx. I Predict the total processing cost if 13,000 units are produced. b. C. Why do we use high low method