A sample of a solid substance of mass 0.20 kg is heated at a constant rate using a heater of power 150 W. The graph shows how the temperature of the substance varies with time.
What is the specific latent heat of fusion of the substance?
90 kJ kg−190\text{ kJ kg}^{-1}90 kJ kg−1
180 kJ kg−1180\text{ kJ kg}^{-1}180 kJ kg−1
270 kJ kg−1270\text{ kJ kg}^{-1}270 kJ kg−1
375 kJ kg−1375\text{ kJ kg}^{-1}375 kJ kg−1