Assuming the mass of the ice in the beaker was 2000 g (2 kg), calculate the amount of heat that must have been added to convert the ice to water (assume that the entire 2000 g was ice at the start of melting, and the entire 2000 g was water at the end of the melting). Assume that the change took place entirely at 0 °C. The heat of fusion (DHfus) for H2O is 6.12 kJ/mol.