The following are monthly actual and forecast demand levels for May Through December for units of a product manufactured by the N. Tamimi Pharmaceutical Company: Month may, june, july, august Sept, Oct, Nov, Dec: Actual Demand 100, 80, 110, 115, 105, 110, 125, 120, and forecast Demand is 100,104,99,101,104,104,105,109. what is the value of the tracking signal as of the end of December?