Figure 1 shows an electric sauna heater.
The heater contains basalt stones.
The stones are heated by electric elements inside the unit.
The heater supplies 150 kJ of thermal energy to each stone.
One basalt stone has a mass of 2.5 kg.
The specific heat capacity of basalt is 800 J/kg∘C800\text{ J/kg}^\circ\text{C}800 J/kg∘C.

Use this data to calculate the temperature increase of the basalt stone.