How would I solve this?

22. High-Low Method. The city of Rockville reported the following annual cost data for maintenance work performed on its fleet of trucks. Reporting Period (Year) | Total Costs | Level of Activity (Miles Driven) Year 1 $ 750,000 225,000 Year 2 850,000 240,000 Year 3 1, 100,000 430,000 Year 4 1, 150,000 454,000 Year 5 1,250,000 560,000 Year 6 1,550,000 710,000 Required: a. Use the four steps of the high-low method to estimate total fixed costs per year and the variable cost per mile. State your results in the cost equation form Y = f + vX. b. What would the estimated costs be if the trucks drove 500,000 miles in year 7