A hydrocarbon feed flowing at a rate of 100 kg/h consisting of a mixture of propane (20%), isobutene (30%), isopentane (20%), and n-pentane (30%) is fractionated in a distillation column. The distillate contains all the propane and 78% of the isopentane in the feed. The mass fraction of isobutene in the distillate is 0.378. The bottom stream contains all the n-pentane fed to the unit. Determine the flow rate of the bottom stream.