Calculate E∘cell for each of the following balanced redox reactions.

Part A: O2(g)+2H2O(l)+4Ag(s) → 4OH−(aq)+4Ag+(aq)

Part B: Br2(l) + 2I−(aq) → 2Br−(aq) + I2(s)

Part C: PbO2(s)+4H+(aq)+Sn(s)→Pb2+(aq)+2H2O(l)+Sn2+(aq)

Part D: Which of the reactions are spontaneous as written.