Solució: \begin{align} E_1 &= \cssId{Step1}{E_1= V·p·C_e·(T_1 - T_0)} \\[3px] &\cssId{Step2}{ E_1= 0,5·1·4,18·10^3(120-20)} \\[3px] &\cssId{Step3}{E_1= 209,0 kJ=58,06 Wh} \\[3px] \end{align}