Density of water at 4\(^\circ\)C is 1000 kg/m\(^3\) and at 20\(^\circ\)C it is 998 kg/m\(^3\). If 4kg of water is heated from 4\(^\circ\)C to 20\(^\circ\)C, the change in internal energy of water is : (Given : specific heat capacity of water = 4200 J/kg K, Atmospheric pressure P = \(10^5\) Pa).