\(V_1 = 320 (e^{-\lambda})==> 240 = 320 (e^{-\lambda})\)
\(==>\) \({e^{ - \lambda }} = \frac{3}{4}\)
\(V_2 = 320 (e^{-\lambda})^2\) \(==>\) \(320 \times {\left( {\frac{3}{4}} \right)^2} = 180\,volt\)
\(V_3 = 320 (e^{-\lambda})^3\) = \(320 \times {\left( {\frac{3}{4}} \right)^3} = 135\,volt\)