ISOM Forecasting question

The Swim Wear Store sells bathing caps. As
the store does not sell a lot of them, such that ordering them periodically
during the year when they run out has been the method of restocking. The store
has the opportunity to purchase them in bulk at a much cheaper price from a
supplier, but the supplier is only willing to ship these once a year. Thus, the
Swim Wear Store needs to predict how many they will need next year. They have
many loyal customers that will be very upset if they are not able to purchase a
swim cap. Swim Wear Store has determined that customers will not be upset if
they cannot purchase swim caps in December, just in case they run out. Swim
Wear Store has kept the monthly sales records of swim caps for the years, 2015,
2016 and 2017. The store would also like to know the monthly sales forecast for
swim caps in 2018, as it will help them to determine sales of other products,
along with the total sales of swim caps for 2018. Follow the steps below.

• Create a numerical reference for each month in the Time column.
• In the column CMA, use the centered moving average for the month.
• In the column seasonal index, (Sales/CMA) for each month.
• Find the seasonal ratio, using the table labeled Seasonal Ratio
• Calculate the deseasonalized demand. (Sales/Seasonal Ratio)
• Use Trend to forecast demand.
• Seasonalize the forecast (TrendX Seasonal Ratio)

How much is the overall demand for bathing caps for 2018? What is the monthly demand?