Consider the Below Data Which Is Based on a Company's

Consider the below data which is based on a company's sales in the period 2000 to 2011 along with the national income of the country, where the business is set up. $$\begin{array} { | c | c | c | } \hline \text { Year } & \begin{array} { c } \text { National Income } \\\text { (in millions of } \\\text { dollars) } \boldsymbol { x }\end{array} & \begin{array} { c } \text { Company's sales } \\\text { (in thousands of } \\\text { dollars) } \boldsymbol { y }\end{array} \\\hline 2000 & 305 & 470 \\\hline 2001 & 316 & 485 \\\hline 2002 & 358 & 499 \\\hline 2003 & 350 & 515 \\\hline 2004 & 375 & 532 \\\hline 2005 & 392 & 532 \\\hline 2006 & 400 & 556 \\\hline 2007 & 398 & 576 \\\hline 2008 & 430 & 583 \\\hline 2009 & 456 & 587 \\\hline 2010 & 578 & 601 \\\hline 2011 & 498 & 605 \\\hline\end{array}$$
a. Develop a scatter chart for these data, treating the national income as the independent variable. Does a simple linear regression model appear to be appropriate?
b. Develop an appropriate estimated regression equation to predict the company's sales, given the national income. How much variation in the sample values of company's sales is explained by this regression model