C# help I could not solve it! how to lower qwality of a ball?

I’m doing a project where a Pet owner can interact with his animals in different ways and I’m stuck. The problem I’m having is with the ball interaction. What I want to do is when using the Fetch() method and then throwing the ball to one of the animals the quality of the ball gets lowered by 2 when interacted with the dog, and by 1 when interacting with the puppy. I’m guessing the ball needs to have a starting value. The problem is that I have no idea how to get the quality to be lowered with each interaction. Could any of you help me?

You have a play routine. Can’t you add to that method for dogs and puppies to decriment the ball quality each time a dog or puppy play with it?

I really don’t know how to do it.