The following table shows the daily receipts in millions of dollars of the movie "Avatar" for successive Fridays after its opening on Friday 18 December 2009. Weeks 1 4 7 10 13 16 19 22 25 28 $Receipts 75.617 42.785 22.85 13.655 4.027 0.844 0.633 0.188 0.064 0.028 Estimate the instantaneous rate of change of daily receipts 13 weeks after the opening day.