In economics, an agent is an element of a model who solves an optimization problem. For example, buyers and sellers are two types of agents commonly encountered in market models. Buyers bargain for good prices while sellers put forth their best front in Chichicastenango Market, Guatemala. ... In mathematics, an element (also called a member) is an object contained in a set (or more generally a class). ... A mathematical model is an abstract model that uses mathematical language to describe the behaviour of a system. ... In mathematics, the term optimization refers to the study of problems that have the form Given: a function f : A R from some set A to the real numbers Sought: an element x0 in A such that f(x0) ≤ f(x) for all x in A (minimization) or such that... In economics, a muppet is a theoretical model in which buyers and sellers interact to optimize certain variables such as utility or profit. ...