\textbf{118-} The natural numbers are grouped in such a way that the number of members in each group (except the first and second groups) equals the sum of the members of the two preceding groups; that is: $\ldots, \{11, 12\}, \{7, 8, 9, 10\}, \{4, 5, 6\}, \{2, 3\}, \{1\}$. What is the average of the members of the thirteenth group?
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(1) $2204.5$ \hfill (2) $3072.5$ \hfill (3) $4350.5$ \hfill (4) $6144.5$
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