Among the following cations, the number of cations which will give characteristic precipitate in their identification tests with K_4[ Fe ( CN )_6] is…

Among the following cations, the number of cations which will give characteristic precipitate in their identification tests with $\displaystyle \mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]$ is $\displaystyle \_\_\_\_$. $$\mathrm{Cu}^{2+}, \mathrm{Fe}^{3+}, \mathrm{Ba}^{2+}, \mathrm{Ca}^{2+}, \mathrm{NH}_4^{+}, \mathrm{Mg}^{2+}, \mathrm{Zn}^{2+} $$