The following half-cells are available:
(i) Ag⁺(aq, 1.0 M) | Ag(s)
(ii) Zn²⁺(aq, 1.0 M) | Zn(s)
(iii) Cu²⁺(aq, 1.0 M) | Cu(s)
(iv) Co²⁺(aq, 1.0 M) | Co(s)

Linking any two half-cells makes a voltaic cell. Given four different half-cells, six voltaic cells are possible. These are labeled, for simplicity, Ag-Zn, Ag-Cu, Ag-Co, Zn-Cu, Zn-Co, and Cu-Co.
(a) In which of the voltaic cells does the copper electrode serve as the cathode? In which of the voltaic cells does the cobalt electrode serve as the anode?
(b) Which combination of half-cells generates the highest potential? Which combination generates the lowest potential?