How many geomatrical isomers are possible for each of the following complexes ?
`(a) [Pt(NH_(3))_(2)(SCN)_(2)] " " (b) [CoCl_(2)Br_(2)]^(2-)("tetrahedral")`
`(c ) [Co(NH_(3))_(3)(NO_(2))_(3)]" " (d) [Pt(en)Cl_(2)]`
`(e ) [CrBr_(2)(en)_(2)]^(+) " " (f) [Rh(en)_(3)]^(3+)`