The Smith-Brinkley (SB) method, is based on an analytical solution of the
(a) Infinite-difference equations
(b) Differential Equations
(c) Integration
(d) Finite-difference equations
I had been asked this question in an international level competition.
This interesting question is from Analysis of Existing Columns with Brinkley Method topic in section Column Process Design, Optimization and Shortcut Calculations of Distillation Design