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247: Mainline

So far, you have learned how you can define classes for two entertainment types: movies and symphonies. Now, suppose that you want to add information that is common to all entertainment types, such as an instance variable, minutes, that records duration.

One way to proceed is to start with the classes that you have already defined for movies and symphonies, adding a minutes instance variable to both classes. If you define movies and symphonies in this way, adding the minutes instance variable to the Movie and Symphony class definitions creates exact duplicates.