Let P be the point of intersection of the three planes $\overrightarrow{r}.\overrightarrow{n_1}=0,\overrightarrow{r}.\overrightarrow{n_2}=1$ and $\overrightarrow{r}.\overrightarrow{n_3}=2$ where $\overrightarrow{n_1},\overrightarrow{n_2}\text{\hspace{0.17em}\hspace{0.17em}and\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}\overrightarrow{n_3}$ are $2\widehat{j}+\widehat{k},5\widehat{i}-12\widehat{j}\text{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}and\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}3\widehat{i}+4\widehat{k}$ respectively. Then the projection of  $\overline{OP}$ on the Z – axis (O being origin) is