The file P12_16.xlsx contains the daily closing prices of American Express stock for an eight-week period.

1. Use the random walk model to forecast the closing price of this stock on the next trading day. Round your answer to the nearest cent, if necessary.

   $

2. You can be about 95% certain that the forecast made in part a will be off by no more than how many dollars? Round your answers to the nearest cent, if necessary.

   	Forecast
   Lower limit	$
   Upper limit	$

   Date	Adjusted Close
   11-Sep-17	84.74
   12-Sep-17	85.59
   13-Sep-17	85.68
   14-Sep-17	85.24
   15-Sep-17	86.03
   18-Sep-17	86.90
   19-Sep-17	88.02
   20-Sep-17	87.45
   21-Sep-17	87.44
   22-Sep-17	87.42
   25-Sep-17	87.23
   26-Sep-17	87.71
   27-Sep-17	88.50
   28-Sep-17	89.14
   29-Sep-17	89.46
   2-Oct-17	89.54
   3-Oct-17	90.42
   4-Oct-17	90.00
   5-Oct-17	90.50
   6-Oct-17	90.89
   9-Oct-17	91.03
   10-Oct-17	91.22
   11-Oct-17	91.29
   12-Oct-17	90.95
   13-Oct-17	92.19
   16-Oct-17	91.29
   17-Oct-17	91.03
   18-Oct-17	91.41
   19-Oct-17	91.23
   20-Oct-17	91.42
   23-Oct-17	91.71
   24-Oct-17	93.18
   25-Oct-17	92.85
   26-Oct-17	95.00
   27-Oct-17	95.10
   30-Oct-17	94.38
   31-Oct-17	94.83
   1-Nov-17	95.10
   2-Nov-17	95.29
   3-Nov-17	95.73