Task: Classify the mental state of the tweeter based on the tweet, determining if it is 'neutral or no emotion' or characterized by any of the provided emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust).
Tweet: @Groupon_UK who do I contact about a shocking experience with Clear Sky Holidays booked through you guys?? #customerservicefail
This tweet contains emotions: 
anger, disgust, sadness