How does coordination compound of type cis [Ma4bc] (where M is central metal; a,bc are monodentate ligands) contains an plane of symmetry

Dear Student,
[Ma4bc] indicates hybridization sp3d2. The structure is octahedral with four particles in a plane and one molecule above and underneath. On the off chance that the iotas a2bc are in the plane and the other two a particles above and beneath the plane, at that point the plane itself is a plane of symmetry.