Solució: \begin{align} E_{dia} &= \cssId{Step1}{ c_{p} · c_{e} · ΔT} \\[3px] &\cssId{Step2}{ E_{solar}=\frac {E_{dia}}{η_{B}}} \\[3px] &\cssId{Step3}{ S_{necessaria} = \frac {E_{solar}/t}{I}} \\[3px] &\cssId{Step4}{ n = \frac {S_{necessaria}}{S}} \\[3px] \end{align}