Detailed Instructions: In this task, you are given a context tweet and an answer. Your job is to generate a question for the given answer based on the given tweet paragraph. Note that your question should be answerable based on the given tweet, and the answer to your question should be the given answer.
Q: Context: Green Line: Service may be impacted Tuesday AM. Trains every 8-10 min with POSSIBLE shuttle bus replacement btwn Navy Yard & Gallery Place. Metrorail Info (@Metrorailinfo) January 13, 2015 Answer: 8-10 min
A:
how often for trains