Coordination Chemistry: Isomerism in Octahedral Complexes

For the octahedral complex [Co(en)2Cl2]+: (a) Draw all possible geometric isomers. (b) Which isomers are chiral (have optical isomers)? (c) Draw the optical isomers. (d) How many total stereoisomers exist? (e) If you replaced en with NH3 (giving [Co(NH3)4Cl2]+), how many stereoisomers would exist and why?