Given the task definition and input, reply with output. In this task, you will be presented with the directions of a recipe separated by "," and have to fill in the "___" which is a step that is missing from the recipe.

Heat oven to 400.,______,Combine flour, wheat germ, sugar, baking powder and cinnamon.,Stir in apples, raisins and nuts.,Add milk, oil and egg and mix just until dry ingredients are moistened.,Fill tins.,Bake 15 to 20 minutes at 400.,Yields 12.
Grease bottom of muffin tins.