How much tin taken at a temperature of 320C can be melted if the melting temperature is 2320C

How much tin taken at a temperature of 320C can be melted if the melting temperature is 2320C, and 840kJ of energy is spent on the whole process?

Q = Q1 + Q2, where Q = 840 kJ = 840 * 10³ J.
Q1 = C * m * (tc – tn), where C is the specific heat of tin (C = 230 J / (K * kg)), m is the mass of tin, tc is the melting point (tc = 232 ºС), tn is the initial temperature (tн = 32 ºС).
Q2 = λ * m, where λ is the specific heat of fusion of tin (λ = 0.59 * 10 ^ 5 J / kg).
Q = Q1 + Q2 = C * m * (tк – tн) + λ * m.
m = Q / (C * (tc – tn) + λ) = 840 * 10³ / (230 * (232 – 32) + 0.59 * 10 ^ 5) = 8 kg.
Answer: You can melt 8 kg of tin.