Gen Chem - Isomers in a complex ion

[elitespart]

How can you know if a complex ion has an optical isomer or not? I understand that it's when the mirror image can't be superimposed but am having trouble recognizing it. For example, take
[Co(NH3)4F2]+. Does this have an optical isomer or just cis/trans?

 

[Borek]

Try to draw it.

 

[elitespart]

right, I did that. but I'm not sure if the NH3s are fixed or if they can move around etc.
I have:
NH3
l
NH3 - Co - NH3
l
NH3

And one F coming out of the screen and the other in the back. So I think it has cis/trans, but I'm not sure about optical.

EDIT: the picture isn't coming out right but the metal has 4 NH3 ligands on surrounding it.