For recentUNdata for several nations, a regression of carbon dioxide use (CO2, a measure of air pollution) on gross domestic product (GDP) has a correlation of 0.786.

With life expectancy as a second explanatory variable, the multiple correlation is 0.787.

(a) Explain how to interpret the multiple correlation.

(b) For predicting CO2, did it help much to add life expectancy to the model? Does this mean that life expectancy is very weakly correlated with CO2? Explain.