When a voltaic cell is constructed from a Ag aq (1.0 molL-1)/Ag (s) half-cell and a standard hydrogen electode, the cell emf is measured to be 0.80V, and the Ag(aq)/Ag(s) half-cell is found to be the cathode. When another cell is composed of a Ag(aq) 1.0 molL-1 Ag(s) half-cell and a Zn2+ (aq 1.0 molL-1)/ An (s) half-cell, the cell emf is measured to be 1.56 V, and the Zn2+ (aq)/Zn(s) half-cell is the anode. What is the reduction potential of the Zn2+ (aq)/Zn(s) half cell?