Listed are the net sales (in millions of euros) for the Adidas Group from 2011 to 2018.

Year                                             Net Sales
2011 . . . . . . . . . . . . . . . . . . . . . . 13,322
2012 . . . . . . . . . . . . . . . . . . . . . . 14,883
2013 . . . . . . . . . . . . . . . . . . . . . . 14,203
2014 . . . . . . . . . . . . . . . . . . . . . . 14,534
2015 . . . . . . . . . . . . . . . . . . . . . . 16,915
2016 . . . . . . . . . . . . . . . . . . . . . . 18,483
2017 . . . . . . . . . . . . . . . . . . . . . . 21,218
2018 . . . . . . . . . . . . . . . . . . . . . . 21,915

a. Determine the index for 2018, using 2011 as the base period.

b. Use the period 2011 to 2013 as the base period and find the index for 2018.

c. Use regression analysis to find the trend equation. What is the estimated consolidated revenue for 2019 and 2020? What is the rate of increase per year?