$7.$ The McCabe$$Thiele method is a graphical technique used for the design of binary distillation columns. Explain the steps involved in this method and how it determines the number of theoretical stages required for a given separation.

$8.$ The Ponchon$$Savarit method offers a different approach to column design compared to McCabe$$Thiele$.$ Discuss the basis of the Ponchon$$Savarit method, focusing on how it incorporates enthalpy$-$concentration diagrams in the analysis.