The feed stream in the table below is to be separated into four nearly pure products. None of the components is corrosive and, based on the boiling points, none of the three separations is difficult. As seen in Figure 1.9, five distillation sequences are possible. 

(a) Determine a suitable sequence of three columns using the heuristics of §1.7. 

(b) If a fifth component were added to give five products, Table 1.8 indicates that 14 alternative distillation sequences are possible. Draw, in a manner similar to Figure 1.9, all 14 of these sequences.

Component Methane Benzene Toluene Ethylbenzene Feed rate, kmol/h 19 263 85 23 Normal boiling point, K 112 353 384 409