Using the High Low Method. Tried already numerous times and not sure how the Professor got 4,000+.50x as the solution? Please help. I chose D, however that apparently was incorrect.

3. 3. The following data pertains to activity and utility cost for two recent periods: Activity level (units) 8,000 5,000 Utility cost $8,000 $6,500 do: J.J Utility cost is a mixed cost with both fixed and variable components. Using the high-low method, the cost formula for utility cost is: Y = $1.00 x Y = $1.25 X Y = $4,000+ $0.50 X Y = $1,500 + $1.25 X