If the mean of the data $7,8,9,7,8,7, \lambda$ and 8 is 8 , then variance of the data is equal to

Based on the following statements, choose the correct option.

Statement I The variance of the first $n$ even natural numbers is $\frac{n^2-1}{4}$.

Statement II The difference between the variance of the first 20 even natural numbers and their arithmetic mean is 112 .

If $x_1, x_2, x_3, \ldots . x_n$ are $n$ observations such, that $\Sigma\left(x_i+2\right)^2=28 n$ and $\Sigma\left(x_1-2\right)^2=12 n$, then the variance is

The coefficient of variation for the frequency distribution is

$$ \begin{array}{|c|l|l|l|} \hline \boldsymbol{x}_{\boldsymbol{i}} & 4 & 3 & 1 \\ \hline \boldsymbol{f}_{\boldsymbol{i}} & 1 & 3 & 5 \\ \hline \end{array} $$