Scala visibility

Let's review the different kind of visibility:

• public: In scala, the public keyword does not exist, this is the default behavior. If nothing is specified, the member of this context will be available for all to call.
• private: This will make the member not visible to the rest of the world (There is an exception about companion object, we are going to learn about it in a future SKB).
• protected: This was not illustrated in this exercise. It is related to object oriented programming and more specifically about inheritance. We are going to learn more about it in a later SKB.