How do I calculate the cell potential (EMF) for Hg(l) + HgCl(aq) -> Hg2Cl2(s)?

[Michew]

Hg^(2+) + 2e- -> Hg : +0.854 V

Hg2Cl2 + 2e- -> 2Hg + 2Cl- : +0.2676 V

Please help! Thanks in advance