$28.$ Describe the graphical method for obtaining Van Laar and Margules constants from vapor$-$liquid equilibrium data.

$29.$ What are the mathematical optimization techniques used for calculating these constants, and how do they improve accuracy?

$30.$ How does the application of nonlinear regression analysis assist in the determination of Margules and Van Laar constants?

$31.$ Discuss the significance of using Van Laar and Margules equations in the design of separation processes.