2025 Fermat Problem 14

A substance doubles its volume every minute. At 9:00 a.m. a small amount of the substance was placed in a large empty container. At 9:20 a.m. the same day, the container became full. At what time was the container one-quarter full?

\textbf{(A)}\ 9:15 a.m.\quad \textbf{(B)}\ 9:10 a.m.\quad \textbf{(C)}\ 9:16 a.m.\quad \textbf{(D)}\ 9:04 a.m.\quad \textbf{(E)}\ 9:18 a.m.

If there are no answer choices shown, enter a numerical answer.

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