The mean deviation about the mean for the following data is \begin{array}{c|l|l|l|l|l} \hline \text { Class interval } & 0-2 & 2-4 & 4-6 & 6-8 & 8-10 \\\\ \hline \text { Frequency } & 1 & 3 & 5 & 3 & 1 \\\\ \hline \end{array}

Assertion (A) The variance of the first $n$ odd natural numbers is $\frac{n^2-1}{3}$.

Reason (R) The sum of the first $n$ odd natural numbers is $n^2$ and the sum of the squares of the first $n$ odd natural numbers is $\frac{n\left(4 n^2-1\right)}{3}$.

Which of the following alternatives is correct?