The cost of 2 Rs/kWh of operating an electric motor for 10 hours takes 10 amp at 110 V is :

l watt = 1J/sec; 1 kwh = $\frac{\mathrm{V}\times \mathrm{I}\times \mathrm{t}\left(\mathrm{hr}\right)}{1000}$
Total kwh =10^-3 x 110 x 10 x 10 = 11
Total cost = 11 x 2 = 22 Rs.