Revenue The graph shows the revenue (in billions of dollars) for AT&T for the years 2009 through 2013. Revenue (in billions of dollars) 130 129 128 127 126 125 124 123 122 m= (9, 123.0) 9 (10, 124.4) 10 (11, 126.7) ---Select--- ---Select--- 11 (12, 127.4) Year (92009) (13, 128.8) 12 (a) Determine the time periods in which the average salary increased the greatest and the least. greatest increase least increase 13 (b) Find the slope, m, of the line segment connecting the points for the years 2009 and 2013. (c) Interpret the meaning of the slope in part (b) in the context of the problem. Revenue increased by one billion dollars every m years between 2009 and 2013. Revenue will increase next year by $m billion exactly. Revenue increased by $m billion between 2009 and 2013. Revenue increased by $m billion each year between 2009 and 2013. Revenue increased an average of $m billion per year from 2009 to 2013.