How many of the following are optically inactive?
i. $\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{s}-{\left[\text{Co}{\left(\text{en}\right)}_2\left({\text{NH}}_3\right)\text{Cl}\right]}^{2+}$
ii. $\mathrm{c}\mathrm{i}\mathrm{s}-{\left[\text{Co}{\left(\text{en}\right)}_2{\text{Br}}_2\right]}^{+}$
iii. $\left[\text{Co}{\left({\text{NH}}_3\right)}_3{\text{Cl}}_3\right]$
iv. $\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{s}-{\left[\text{Co}{\left({\text{NH}}_3\right)}_4{\text{Cl}}_2\right]}^{+}$
v. $\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{s}-{\left[{\text{CoCl}}_2{\left({\text{C}}_2{\text{O}}_4\right)}_2\right]}^{3-}$

Hence, the correct answer is 4.00.