Моето решение: 
StartUp - https://pastebin.com/7eZbVR8r
class Rabbits - https://pastebin.com/Rgai1NxM
class Cagr - https://pastebin.com/H5CGePLv

  
Условие:
Your task is to create a repository which stores rabbit cages by creating the classes described below.
First, write a C# class Rabbit with the following properties:

• Name: string
• Species: string
• Available: bool - true by default

The class constructor should receive name and species. Override the ToString() method in the following format:

"Rabbit ({species}): {name}"

Next, write a C# class Cage that has data (a collection which stores the entity Rabbit). All entities inside the repository have the same properties. Also, the Cage class should have those properties:

• Name: string
• Capacity: int

The class constructor should receive name and capacity, also it should initialize the data with a new instance of the collection. Implement the following features:

• Field data - collection that holds added rabbits
• Method Add(Rabbit rabbit) - adds an entity to the data if there is room for it
• Method RemoveRabbit(string name) - removes a rabbit by given name, if such exists, and returns bool
• Method RemoveSpecies(string species) - removes all rabbits by given species
• Method SellRabbit(string name) - sell (set its Available property to false without removing it from the collection) the first rabbit with the given name, also return the rabbit
• Method SellRabbitsBySpecies(string species) - sells (set their Available property to false without removing them from the collection) and returns all rabbits from that species as an array
• Getter Count - returns the number of rabbits
• Report() - returns a string in the following format, including only not sold rabbits: 
  • "Rabbits available at {cageName}:
    {Rabbit1}
    {Rabbit2}
    (…)"

Constraints

• The names of the rabbits will be always unique.
• You will always have a rabbit added before receiving methods manipulating the Cage’s rabbits.