The table shows the number of people in North America who use email as a part of their jobs. North American Business Email Users Email Users, n1 Year (million users) 2005 127.3 2006 130.9 2008 135.1 2009 138.4 2010 140.4 (a) Write the function for the linear model that gives the number of North American business email users in millions, where x is the number of years since 2005, with data from 0 s x s 5. (Round all numerical values to three decimal places.) 2007 134.7 m(x) = million users (b) What is the constant rate of change of the number of North American business email users? (Round your answer to three decimal places.) million users per year (c) Use the model to estimate the number of North American business email users in 2012. (Round your answer to three decimal places.) million users Is this estimate found by interpolation or extrapolation? O interpolation O extrapolation