Task: Analyze the tweet's emotional connotations and classify it as either 'neutral or no emotion' or as one or more of the specified emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust) that best portray the tweeter's mental state.
Tweet: @Rocks_n_Ropes Can't believe how rude your cashier was today when I was returning an item!  Your customer service is slacking.
This tweet contains emotions: 
anger, disgust, sadness