The emf of cell \(Tl\left|\underset {(0.001M)}{Tl^+}\right|\left|\underset {(0.01M)}{Cu^{2+}}\right| Cu\) is 0.83 V at 298 K. It could be increased by
(1) increasing concentration of \(Tl^+\) ions
(2) increasing concentration of both \(Tl^+\) and \(Cu^{2+}\) ions
(3) decreasing concentration of both \(Tl^+\) and \(Cu^{2+}\) ions
(4) increasing concentration of \(Cu^{2+}\) ions