Q68. Let $\alpha , \beta \in \mathbf { R }$. Let the mean and the variance of 6 observations $- 3,4,7 , - 6 , \alpha , \beta$ be 2 and 23 , respectively. The mean deviation about the mean of these 6 observations is :\\
(1) $\frac { 13 } { 3 }$\\
(2) $\frac { 16 } { 3 }$\\
(3) $\frac { 11 } { 3 }$\\
(4) $\frac { 14 } { 3 }$