Question 7

The Accuweather Corporation manufactures barometers and thermometers for weather forecasters. In an attempt to forecast its future needs for mercury, Accuweather's chief economist estimated average monthly mercury needs as:

N = 500 + 10X

where N = monthly mercury needs (units) and X = time period in months (January 2020= 0). The following monthly seasonal adjustment factors have been estimated using data from the past five years:

Month Adjustment Factor

January 15%

April 10%

July -20%

September 5%

December -10%

(a)Forecast Accuweather's mercury needs for January, April, July, September, and December of 2022.

(b)The following actual and forecast values of mercury needs in the month of November have been recorded:

Year Actual Forecast

2021 456 480

2020 324 360

2019 240 240

What seasonal adjustment factor should the rm use for November?