A major sausage producer has an office in Wolfsburg, Germany. The sales manager of the office is evaluated based on the number of new clients signed up every quarter. The following data reflects the number of new customers added during each quarter between 2016 and 2019.

Year	Quarter	No. of Clients
2016	1	555
2016	2	569
2016	3	522
2016	4	623
2017	1	589
2017	2	624
2017	3	601
2017	4	670
2018	1	631
2018	2	704
2018	3	673
2018	4	755
2019	1	721
2019	2	771
2019	3	769
2019	4	844

a. Calculate the multiple linear regression equation using quarterly data as dummy variables. (6 marks) b. Interpret each slope and the intercept in the multiple linear regression equation from part a. Calculate a 90% confidence interval for each variable slope and assess whether it is statistically significant. (6 marks) c. Create a forecast for 2020 and 2021. (3 marks)