Maths problem: why answer is b, I calculated many times, thanks?

From time t = 0 to t = 10, the amount of heat energy absorbed by the substance P is
1.5 × 2000 × (130 - 40) = 270000 J.

Therefore, the power of the heater is (270000 J) / (10 min) = 27000 J/min.

The substance absorbs heat energy during the state between solid and liquid for 40 - 10 = 30 minutes, so it absorbs 27000 × 30 = 810000 J.

Per 1.5 kg, the specific latent heat of fusion of substance P is
(810000 J) / (1.5 kg) = 540000 J/kg = 5.40 × 10⁵ J kg⁻¹.

The answer is C.

前 10 分鐘溫度從 40°C 上升到 130°C,
需要熱量 2000 × (130-40) × 1.5 = 270(kJ ).
所以後30分鐘, 依比例計算, 共需要熱量 810kJ.
所以, 每 kg 融解熱是
   810 ÷ 1.5 = 540 (kJ/kg) = 5.4×10^5 J/kg