An ellipse is the locus of all points which have the constant sum of distances from 2 fixed points (=focus).

Therefore:

1. (0, -5), (0, 5) are the focii.

2. The sum of distances is 20. (The distance between the focii is 10!)

3. The length of the main semiaxis must be 10.

4. The center of the ellipse must be the origin.

5. The length of the minor semi axis must be: