Sales of a product for the last three years are given below

Year	Jan	Feb	Mar	April	May	June	Jul	Aug	Sep	Oct	Nov	Dec
1	800	795	815	800	805	812	820	830	825	820	810	800
2	802	795	812	802	804	814	825	835	824	814	808	798
3	798	800	810	804	806	816	826	834	822	816	810	804

i) Find the seasonal index for each of the months.

ii) Considering the available data for the last three years find the least square regression line y = a + b x, where

iii) Using the regression line found in ii) determine 4th year demand.

iv) Forecast the rounded-off monthly demand for each of the months of year 4.

b=x2nx2xynxy;a=ybx