How to solve this error

Question

https://code.sololearn.com/c84BD3Me8iUC/?ref=app

Answer 1

Yes little mistake

Answer 2

https://code.sololearn.com/cux1NVBFWfSN/?ref=app

Answer 3

Your extending Dod1 instead of Dog
line no: 42 , Use
class FDog extends Dog { //not Dog1
...
}
Dog1 is your main class..