For planning production in the medium term, vehicle manufacturers need to forecast tire demand for new motor vehicle sales. The following data are the number (in thousands) of Honda Ridgeline trucks manufactured by Honda during each quarter, starting from first quarter of 2005 (when Ridge line was introduced) until the 3rd quarter of 2008. Assume that all Ridgelines produced in a quarter were sold in the same quarter.

a. Compute the seasonal relative for each quarter using the centred moving average method.
b. Deseasonalize the data, fit an appropriate model to the deseasonalized data, extend the model four quarters, and reseasonalize these in order to forecast the sales of Ridgeline trucks in the 4th quarter of200S, and I st, 2nd, and 3rd quarters of 2009.

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Year 2005 2006 2007 2008 Q1 11.5 11.9 10.0 10.2 Q2 19.2 15.1 19.1 6.2 Q3 17,4 174 13.9 5.6 Q4 12.7 12.1 11.5