A 100 g sample of lead, initially solid at room temperature, is heated. By 22 s, it has completely melted. The graph plots how the temperature changes with time. The heater has a power of 320 W. Which expression gives the specific latent heat, in J kg$^{-1}$, for the lead?
- A$\dfrac{7.0 \times 320}{0.10 \times 300}$
- B$\dfrac{22 \times 320}{0.10 \times 300}$
- C$\dfrac{7.0 \times 320}{0.10}$
- D$\dfrac{22 \times 320}{0.10}$