Using the TGT Quarterly Sales (Target Corp.) data:

a. Fit a regression model with a time trend and seasonal dummy variables to the sales data.

b. Is the time trend coefficient statistically significant? How can you tell?

c. Are the seasonal dummy variables statistically significant? How can you tell?

I need an answer to C. Not sure how Dummy variables are significant

Date	Sales
Sep-11	16,402
Dec-11	21,288
Mar-12	16,867
Jun-12	16,779
Sep-12	16,929
Dec-12	22,726
Mar-13	16,706
Jun-13	17,117
Sep-13	17,258
Dec-13	21,515
Mar-14	17,050
Jun-14	17,406
Sep-14	17,732
Dec-14	21,751
Mar-15	17,119
Jun-15	17,427
Sep-15	17,613
Dec-15	21,626
Mar-16	16,196
Jun-16	16,169
Sep-16	16,441
Dec-16	20,690
Mar-17	16,017
Jun-17	16,429
Sep-17	16,667
Dec-17	22,766
Mar-18	16,781
Jun-18	17,776
Sep-18	17,821
Dec-18	22,977
Mar-19	17,627