c
\(\text { Power }=220\, \mathrm{V} \times 4\, \mathrm{A}=880\, \text { watts. }=880\, \mathrm{J} / \mathrm{s}\)

Heat needed to raise the temperature of \(1\,kg\) water through \(80\,^{o} \mathrm{C}\) 

\( = ms.\,\Delta T \times 4.2\,{\rm{J}}/{\rm{cal}}\)

\( = 1000\,{\rm{g}} \times 1\,{\rm{cal}}/{\rm{g}} \times 80 \times 4.2\,{\rm{J}}/{\rm{cal}}\)

\( \therefore \)  Time taken  \({=\frac{1000 \times 1 \times 80 \times 4.2}{880}=\frac{336 \times 10^{3}}{880}} \) 

\({=382\, \mathrm{s}=6.3\, \mathrm{min}}\)