The emf of cell is \( 0.83 \, \mathrm{V} \) at \( 298 \, \mathrm{K} \). It could be increased by:
increasing concentration of both \( \mathrm{Tl^+} \) and \( \mathrm{Cu^{2+}} \) ions
decreasing concentration of both \( \mathrm{Tl^+} \) and \( \mathrm{Cu^{2+}} \) ions
increasing concentration of \( \mathrm{Cu^{2+}} \) ions
increasing concentration of \( \mathrm{Tl^+} \) ions