Banana Crumb Muffins

3 cups flour
2 teaspoons baking soda
2 teaspoons baking powder
1 teaspoon salt
6 bananas, mashed
1 1/2 cups white sugar
2 eggs, lightly beaten
2/3 cup butter, melted
2/3 cup packed brown sugar
4 tablespoons flour
1/4 teaspoon ground cinnamon
2 tablespoon butter

1. Preheat oven to 375 degrees. Lightly grease muffin cups, or line with muffin papers.
2. In a large bowl, mix together 3 cups flour, baking soda, baking powder and salt. In another bowl, beat together bananas, white sugar, egg and melted butter. Stir in the flour mixture just until moistened. Spoon batter into prepared muffin cups.
3. In a small bowl, mix together brown sugar, 4 tablespoons flour and cinnamon. Cut in 2 tablespoon butter. Top each muffin with a spoonful of sugar mix.
4. Bake for 18 to 20 minutes, until a toothpick inserted into center of a muffin comes out clean.