Hi Kenji, thank you for your alertness. However, the exact density of alcohol is not 800g/L, but actually 789.24 g/L. Hence, your calculation has to be: 350 x 0.09 x 0.78924 = 24.86106. Please find this information verified here: https://en.m.wikipedia.org/wiki/Alcohol_by_volume
Kind regards, Felix