A 70kg human with body temperature of 40°C drinks 1 liter of cold water at 2°C to help cool down. Given that the average specific heat capacity of the human body is 3.6kJ/kg°C, calculate the decrease in the person's average body temperature as a result of consuming this cold water. Assume density of water is 1kg/L and heat capacity is 4.18kJ/kg°C.