Answer
See the explanation
Work Step by Step
a) Each combination of letters and numbers is paired with exactly one element from the machine. Therefore the relation that pairs letter-number combinations with food or drink items is a function.
b) The $\textbf{independent variable}$ is the combination letter-number, while the $\textbf{dependent variable}$ is the food or drink item.
c) The $\textbf{domain}$ of the function is the set of values of the independent variable: $$\{A1,A2,A3,B1,B2,B3,B4,C1,C2,C3,C4\}.$$ The $\textbf{range}$ of the function is the set of values of the dependent variable: the food and drink items in the machine.
