If $\alpha,\beta, \gamma$ are the roots of the equation $x^3-6x^2+11x+6=0,$ then $\sum \alpha^2 \beta+ \sum \alpha \beta^2$ is equal to :

Question

$$\begin {array} {1 1} (a)\;80 & \quad (b)\;84 \\ (c)\;90 & \quad (d)\;-84 \end {array}$$