8. Bell Greenhouses has estimated its monthly demand for potting soil to be the following: N = 400 + 4X where N = monthly demand for bags of potting soil X = time periods in months (March 2006 = 0) Assume this trend factor is expected to remain stable in the foreseeable future. The following table contains the monthly seasonal adjustment factors, which have been estimated using actual sales data from the past five years: MONTH ADJUSTMENT FACTOR (%) March +2 June +15 August +10 December -12b. If the following table shows the forecasted and actual potting soil sales by Bell Greenhouses for April in five different years, determine the seasonal adjustment factor to be used in making an April 2008 forecast