A water heater of power \( 2000 \, \text{W} \) is used to heat water. The specific heat capacity of water \( 4200 \, \text{J kg}^{-1}\text{K}^{-1} \). The efficiency of heater is \( 70\% \). Time required to heat \( 2 \, \text{kg} \) of water from \( 10^\circ\text{C} \) to \( 60^\circ\text{C} \) is ______ s. (Assume that the specific heat capacity of water remains constant over the temperature range of the water)
