Definition: Given a 'poster' sentence and a corresponding 'response' (often, from Facebook or Reddit)classify the sentiment of the given response into four categories: 1) Positive, 2) Negative, 3) Neutral, and 4) Mixed if it contains both positive and negative.
Input: Poster: .@MaddowBlog: Cantwell & Dem Senators want answers from @BarackObama on decision against over the counter Plan B http://bit.ly/tbNg5W  Responser: Thank you for having our backs on these issues.
