The scatterplot shows the gross domestic product (GDP) of the United States in billions of (2013) dollars

Question:

The scatterplot shows the gross domestic product (GDP) of the United States in billions of (2013) dollars plotted against years since 1950.

A linear model fit to the relationship looks like this:
Dependent variable is: GDP
R-squared = 98.3% s = 553.2
Variable Coefficient
Intercept ……………….. 2058.981
Year-1950 ……………… 227.176
a) Does the value 98.3% suggest that this is a good model? Explain.
b) Here's a scatterplot of the residuals. Now do you think this is a good model for these data? Explain?