Consider the PCM distillation column module of Appendix H. Assume that distillate MeOH composition x_D is the output variable and reflux ratio R is the input variable.
Do the following:

1. Develop a first-order plus time-delay (FOPTD) transfer function model from response data for a step change in R at t = 10 min from 1.75 to 2.0. Summarize your calculated model parameters in a table and briefly describe the method used to calculate them.
2. Repeat (a) for a second-order plus time-delay (SOPTD) model.
3. Plot the actual x_D response and the two model responses for the R step change of part (a).
4. Are the two models reasonably accurate? Which model is better? Justify your answer by considering the least square residuals for the one-step ahead prediction errors,