If $a, \bar{b}, \bar{c}$ are three vectors $(\bar{a}-\bar{b}) \times(\bar{a}-\bar{b}-\bar{c}) \cdot(\bar{a}+2 \bar{b}-\bar{c})$ is equal to
(a) $-\left[\begin{array}{lll}a & \bar{b} & \bar{c}\end{array}\right]$
(b) $\left[\begin{array}{lll}- & \bar{b} & \bar{c}\end{array}\right]$
(c) $2\left[\begin{array}{lll}a & \bar{b} & \bar{c}\end{array}\right]$
(d) $3\left[\begin{array}{l}\bar{a} \overline{\mathrm{b}} \overline{\mathrm{c}}]\end{array}\right]$