Economists use the concept of to measure the satisfaction a person gets from the use or consumption of goods and services.

utility is the answer i have founded .

  Economists use the concept of Utility to measure the satisfactions a person gets from the use or consumption of goods and services.

  It´s usage has evolved over time. At first the term was introduced by moral philosopher within the theory of utilitarianism as a way to measure pleasure or satisfaction. But the term has been readapted with the neoclassical economies as a utility function and represents the preference of a consumer over a choice set.

  I hope this answer help you.

the crusaders are identified in the painting;

c. by the red crosses on their backs