Answer:
a. working backward.
Step-by-step explanation:
Working backwards: In psychology, the term "working backwards" is considered as one of the different types of heuristics and is described as a problem-solving method whereby a person imagines or thinks that he or she has solved a specific problem which he or she was trying to solve for quite a while.
Through the process of analyzing or imagining that the person has already solved a specific problem, he or she can then "work backwards" in his or her mind and therefore becomes capable of visualizing a particular solution to the given problem.
In the question above, Millie's strategy most closely resembles the problem-solving heuristic of "working backwards".