Sky, Earth, Ocean

The boxes below represent Sky, Earth and Ocean. Each box has four sections. Look at the list of things below and decide which box should contain each item, then put the number of that item in the box; for example, the first item, Mars, goes in the sky, so you write a 2 in the Sky box. When you have finished, the numbers in each box will add up to 30 if all your placements are right.