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