Nernst Calculations

When the Pb2+ concentration is 1.32M, the observed cell potential at 298K for an electrochemical cell with the following reaction is 0.679V. What is the Cr3+ concentration? 3Pb2+(aq)+2Cr(s)3Pb(s)+2Cr3+(aq)[Cr3+]= When the Pb2+ concentration is 4.05104M, the observed cell potential at 298K for an electrochemical cell with the following reaction is 1.431V. What is the Al3+ concentration? 3Pb2+(aq)+2Al(s)3Pb(s)+2Al3+(aq)[Al3+]= When the Pb2+ concentration is 6.65104M, the observed cell potential at 298K for an electrochemical cell with the following reaction is 0.958V. What is the Mn2+ concentration? Pb2+(aq)+Mn(s)Pb(s)+Mn2+(aq)[Mn2+]=