Determine the valence intensity of the following tweet, considering the mental state of the author. Assign a real number between 0 and 1, where 0 denotes extremely negative and 1 denotes extremely positive.
Tweet: @musicfae15 [He grumbled as he sat atop the sushi bar stool, crossing his arms defiantly, in a playful gesture, though he gave anyone who &gt;
0.550