Stats question, looking for explanation on how to solve?

Hi all, i already have the answers, but i keep getting it wrong, can you please explain to me to solve these? I provided the correct answers.

The Appliance Centre sells a variety of electronic equipment and home appliances. For the last four years, the following quarterly sales (in $ millions) were reported:

Quarter
Year 1 2 3 4
2011 $5.3 $4.1 $6.8 $6.7
2012 4.8 3.8 5.6 6.8
2013 4.3 3.8 5.7 6.0
2014 5.6 4.6 6.4 5.9

Seasonal index for each of the four quarters follows.

Quarter Seasonal
Index
1 0.9067
2 0.7600
3 1.1249
4 1.2085

a. Use the seasonal indexes to determine the deseasonalized sales. Determine the linear trend equation based on the quarterly data for the four years. (Do not round the intermediate calculations. Round the final answers in millions of dollars to 4 decimal places.)

Solve
Y' = ______ – ________t.

Y' = 5.4893 ± 0.0005 – 0.0112 ± 0.0005t.

b. Forecast the seasonally adjusted sales for 2015. (Round the intermediate calculations and the final answers in millions of dollars to 4 decimal places.)

Quarter Forecast
1 4.8045 ± 0.0001

2 4.0187 ± 0.0001

3 5.9355 ± 0.0001

4 6.3631 ± 0.0001