[ Diet & Fitness ] Open Question : How much weight do you think I could lose?

I've been trying to lose weight all summer D: i eat about 250-300 calories a day (a banana for breakfast & either special k with fat free soy milk or a piece of wheat bread with a slice of fat free turkey breast for lunch and no dinner) and drink only water i do about an hour to an hour and a half of cardio (walking) throughout the day and i do about 100 situps in the morning and 100 at night.. any estimation..? thanks