Final answer:
The question cannot be accurately answered with the information provided; 'k' value alone is not sufficient to determine the change in temperature without additional context and properties like specific heat and mass.
Step-by-step explanation:
The change in temperature of the metal sword when transferred from a furnace at 300°C to oil at 20°C depends on the heat exchange and the specific physical properties of the metal and the oil, which include the specific heat capacities and the masses involved. Without the specific heat capacities and masses, the value of 'k' provided does not directly help in calculating the change in temperature. Since the provided value of 'k' (0.15) lacks context and the necessary background in thermodynamics or heat transfer, we cannot accurately determine the change in temperature just from the information given.