= = 4.7 A single equilibrium stage in a distillation column is shown in Fig. E4.7. The model that describes this stage is dH = Lo + V2 - (L1 + V1) dt dHxi Loro + V2y2 - (L1X1 + V1y) dt y1 = 20 + 21x1 + a2x + azxi (a) Assuming that the molar holdup H in the stage is con- stant and that equimolal overflow holds, for a mole of vapor that condenses, one mole of liquid is vaporized, simplify the model as much as possible. (b) Linearize the resulting model and introduce deviation variables. (c) For constant liquid and vapor flow rates, derive the four transfer functions relating outputs x1 and y1 to inputs xo and y2. Put in standard form