Thank you for reporting, we will resolve it shortly
Q.
Let $\vec{a}$ and $\vec{b}$ be two vectors, Let $|\vec{a}|=1,|\vec{b}|=4$ and $\vec{a} \cdot \vec{b}=2$. If $\vec{c}=(2 \vec{a} \times \vec{b})-3 \vec{b}$, then the value of $\vec{b} \cdot \vec{c}$ is
$\vec{ c }=(2 \vec{ a } \times \vec{ b })-3 \vec{ b } $
$ \vec{ b } \cdot \vec{ c }=\vec{ b } \cdot(2 \vec{ a } \times \vec{ b })-3 \vec{ b } \cdot \vec{ b }$
$ =-3| b |^2 $
$ =-48$