Given the total gas mileage and the average speed, Dr. Lane would like to predict the cost it will take to maintain his car throughout the year. The constant/intercept (a) is 150. The b-weight (b1) for the number of miles driven per year is equal to .05. The b-weight (b2) for the average driving speed is 1.40. 7. Use this regression equation Y = a + b1X1 + b2X2 to predict the cost it will take to maintain a car that's been driven 8,000 miles per year (X1) and is typically driven at an average of 55 miles per hour (X2