An iron rod of mass 2kg and at a temperature of 280^oC is dropped into some quantity of water initially at a temperature of 30^oC. lf the temperature of the mixture is 70^oC, calculate the mass of the water. (Neglect heat losses to the surroundings). Specific heat capacity of iron = 460 J kgK) (Specific heat capacity of water = 4200 Jkg K)