2. You are interested in estimating the effect of rainfall on umbrella sales. You obtain on annual rainfall and umbrella sales from 75 cities in 2013. You estimate the follo regression equation, where r; is millimetres of rain in 2013 in city i (in hundreds y is 2013 umbrella sales in city i (in hundreds): yi = bi + bar; + ei Use the following information to answer parts (a)-(d): y = 27.9 I = 10.0 e; = -3.9 when a; = 15 and y; = 40 var (bi ) = 0.0588 N = 15, 675.4 (a) (4 pts) Calculate by and interpret its meaning. (b) (4 pts) Calculate by and interpret its meaning