A researcher records the age x of eight cars, in years, and the repair cost y of each in hundreds…

A researcher records the age $x$ of eight cars, in years, and the repair cost $y$ of each in hundreds of rupees. She does not keep the individual values, only the totals: $n = 8$, $\sum x = 76$, $\sum y = 129$, $\sum xy = 1324$, $\sum x^2 = 820$ and $\sum y^2 = 2187$. Find the three quantities $n\sum xy - \sum x\sum y$, $n\sum x^2 - \left(\sum x\right)^2$ and $n\sum y^2 - \left(\sum y\right)^2$, and then find $r$.