3. Below are some data from a local pizza parlor on gross sales (SALES), promotion dollars (PROMO) and type of promotion used. The parlour uses only 3 types of promotions: -Radio, flyers and newspapers. The parlor used only one type of promotion in any given week. The variables Type1 and Type2 have been coded:

TYPE1 = 1 if radio was used, 0 otherwise

TYPE2 =1 if flyer was used, 0 otherwise

(Hint: This is a problem of dummy variable)

SALES in ('100s)	Promo in 100s	TYPE1	TYPE2
12.1	3.8	0	1
19.1	6.4	0	1
26.9	7.9	0	0
24.8	8.7	1	0
37.1	12.4	1	0
39.4	15.9	0	1
32.5	11.3	0	0
28.9	9.4	0	0
28.8	8.6	1	0
34.7	12.7	0	1
38.4	14.3	0	0
26.3	6.7	1	0

1. Predict sales from Promo, type 1 and type 2 and state the fitted regression equation
2. If Promo is held constant (controlling for promo) is there a significant difference between radio and newspaper at 5% significance level
3. If Promo is held constant (controlling for promo) is there a significant difference between flyer and newspaper at 5% significance level
4. What is the sales when $800 dollar is spent in advertisements through radio advertisements? Calculate 90% confidence interval.