a. find the seasonal index for each quarter

b. find seasonally adjusted demand forecast for each quarter and year 6 

(3) The Great Northwest Outdoor Company is a catalog sales operation that specializes in outdoor recreational clothing. Demand for its items is very seasonal, peaking during the holiday season and during the spring. It has accumulated the following data for orders per season (quarter) during the past five years. Orders (1,000s) Year 1 Year 2 Year 3 Year 4 Year 5 Winter (Q 1) 18.6 18.1 22.4 23.2 24.5 Spring (Q2) 23.5 24.7 28.8 27.6 31.0 Summer (Q 20.4 19.5 21.0 24.4 23.7 3) Fall (Q4) 41.9 46.3 45.5 47.1 52.8 Total 104.4 108.6 117.7 122.3 132.0 Develop a seasonally adjusted forecast model for these order data. Forecast demand for each quarter for year 6, using the annual trend line as given: Y(t) = 96.33 + 6.89t