The mean of the numbers $ a, b, 8, 5, 10$ is $6$ and the variance is $6.80$. Then which one of the following gives possible values of $a$ and $b$ ?

Question

$\begin {array} {1 1} (A)\;a=0\: b=7 & \quad (B)\;a=5\: b=2 \\ (C)\;a=1\: b=6 & \quad (D)\;a=3\: b=4 \end {array}$