If a =2 i + j +3 k, b =3 i +3 j + k and c =c_1 i +c_2 j +c_3 k are coplanar vectors and a · c =5, b ⊥ c, then 122(c_1+c_2+c_3) is equal to \ \ \ \.

If $\displaystyle \vec{a}=2 \hat{i}+\hat{j}+3 \hat{k}, \vec{b}=3 \hat{i}+3 \hat{j}+\hat{k}$ and $\displaystyle \vec{c}=c_1 \hat{i}+c_2 \hat{j}+c_3 \hat{k}$ are coplanar vectors and $\displaystyle \vec{a} \cdot \vec{c}=5, \vec{b} \perp \vec{c}$, then $\displaystyle 122\left(c_1+c_2+c_3\right)$ is equal to \_\_\_\_.