When heat (q) is absorbed by "m" grams of a substance then the change in temperature is given as,
q = m Cp (T₂ - T₁) --- (1)
where;
Cp = Specific Heat
Specific heat of Iron is 0.448 J/g.°C
Initial Temperature = T₁ = 25 °C
Final Temperature = T₂ = 345 °C
Mass of Iron = m = 875 g
Putting values in eq.1,
q = 875 g × 0.448 J/g.°C × (345 °C - 25 °C)
q = 1254400 J
Or,
q = 1.25 × 10⁶ J