A 0.5kg block of an unknown substance is heated by a 200W heater. The temperature rises steadily from −10∘C to 0∘C in 100s and then remains at 0∘C for 300s until the entire mass melts. What is the latent heat of fusion of the substance?
a) 1.6×105Jkg−1
b) 1.2×105Jkg−1
c) 6.0×104Jkg−1
d) 2.4×105Jkg−1