Let a and b be two vectors, Let | a |=1,| b |=4 and a · b =2. If c =(2 a × b )-3 b, then the value of b · c is

Let $\displaystyle \vec{a}$ and $\displaystyle \vec{b}$ be two vectors, Let $\displaystyle |\vec{a}|=1,|\vec{b}|=4$ and $\displaystyle \vec{a} \cdot \vec{b}=2$. If $\displaystyle \vec{c}=(2 \vec{a} \times \vec{b})-3 \vec{b}$, then the value of $\displaystyle \vec{b} \cdot \vec{c}$ is