Let\(\overrightarrow{ a }=2 \hat{i}-7 \hat{j}+5 \hat{k}, \overrightarrow{ b }=\hat{i}+\hat{k} and \overrightarrow{ c }=\hat{i}+2 \hat{j}-3 \hat{k}\) be three given vectors If \(\overrightarrow{ r }\) is a vector such that\( \vec{r} \times \vec{a}=\vec{c} \times \vec{a} \ and \ \vec{r} \cdot \vec{b}=0,\) then \(|\vec{r}|\) is equal to :