The feed to a distillation column operating at 270 lb /in. 2 absolute contains 10 percent

The feed to a distillation column operating at 270 lb_ƒ/in.² absolute contains 10 percent ethane, 45 percent propane, 30 percent i-butane, and 15 percent n-butane, Calculate the bubble point of the feed and the fraction vaporized when the liquid enters the column if the feed is heated as a liquid 20°C above the bubble point.