An object, along with the light source, is 5 cm to the left of an unknown optical element as shown below. The optical element generates an image 15cm to the right of the optical element.

1. What is the object distance o if the optical element is a lens?
2. What is the object distance i if the optical element is a lens?
3. What is the object distance o if the optical element is a mirror?
4. What is the object distance i if the optical element is a mirror?

15cm Image Unknown optical element 5cm