I've been at this for well over an hour now. 5. The speed method must return a Double and accept one CanFly argument 5. The CanFly interface must declare a speed method with one CanFly parameter and must return a Double. 5. The CanFly interface must declare a speed method with one CanFly parameter and must return a Double. Recommendation from mentor There must be a speed method in the CanFly interface and it must not accept arguments. line 9, line 16, and verify step 5 appear to be in direct conflict with the recommendation from the mentor. I need a clear reference of what exactly a CanFly argument / CanFly parameter is, and how it can be passed against itself. I've been all over google, and the previous lessons, and I haven't found anything useful. I need an example, a reference document, or an extended explanation.