What is the rate law for the following reaction and its mechanism?

What is the rate law for the following reaction and its mechanism? 

2 HgCl2 + C2 O4 2- → 2 Cl- + 2 CO2 + Hg2 Cl2 (overall reaction) 
HgCl2 + C2 O4 2- ⇌ HgCl2 C2 O4 2- (fast) 
HgCl2 C2 O4 2- + C2 O4 2- → Hg + 2 C2 O4 Cl2-(slow) 
Hg + HgCl2 → Hg2 Cl2 (fast) 
2 C2 O4 Cl2- → C2 O4 2- + 2Cl- + 2 CO2 (fast) 
A.Rate = k[HgCl2][C2O42-]2
B.Rate = k[Hg2Cl2] 
C.Rate = k[HgCl2]2[C2O42-]2 
D.Rate = k[HgCl2][C2O42-] 
E.Rate = k[HgCl2]2[C2O42-]