Greene Enterprises has the following information about its truck fleet miles and operating costs: Year Miles Operating Costs 2018 400,000 $250,000 2019 480,000 280,000 2020 560,000 320,000 a. Determine the high point and the low point (2.5 points). b. Calculate the variable cost per mile using the high-low method (2.5 points). c. Calculate the fixed costs (2.5 points). d. What is the best estimate of total costs using the high-low method if the expected fleet mileage for 2021 is 500,000 miles? (2.5 points)