In Formulating a Coffee Blending Problem Where There Are Three $X_{1}, X_{2}$

Multiple Choice

In formulating a coffee blending problem where there are three types of coffee beans, the objective is to find a recipe to make 1 pound of blended coffee that satisfies a set of properties at the least cost. The decision variables are $X_{1}, X_{2}$ , and $X_{3}$ , representing pounds (actually fractional pounds) of coffee beans used per pound of blended coffee. One of the constraints of the problem will be

A) $X_{1}+X_{2}+X_{3}<1.0$
B) $X_{1}+X_{2}+X_{3}>1.0$
C) $X_{1}+X_{2}+X_{3}=1.0$
D) no such constraint is required