In order to solve this problem, use the following equations and steps shown: \begin{align} &\cssId{Step1}{c_{inv} = n · {c_{light}} + {c_{inst}}}\\[3px] &\cssId{Step2}{c_{inv} = 197,000euros}\\[3px] &\cssId{Step3}{Δt = \frac{c_{inv}}{c_{save}}}\\[3px] &\cssId{Step4}{Δt = \frac{197,000}{24,842}}\\[3px] &\cssId{Step5}{Δt = 7.93011834796years}\\[3px] \end{align}