Answer:
ACDBA, $900
Step-by-step explanation:
The cheapest route will be the one with the lowest cost. Of the routes listed, the cost $900 is the lowest, so route ACDBA is the cheapest.
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The "Brute Force Method" requires you compute the costs of the possible routes and pick the lowest. The answer choices have done that for you.
The cost of ACDBA is AC +CD +DB +BA = 240 +230 +210 +220 = 900, as shown in the answer selections.
The three routes listed, and their reverses (which are the same cost), are the only possible routes starting and ending at A.