This is an interview question for junior ruby developer @ Fandnext.

1. Clone this project to your local environment
2. Run bundle install in the project folder and make sure all the dependencies have been installed successfully.
3. Run ruby test/price_calculation_test.rb to see if you can run the test. You should see 6 failed test cases.
4. Take a look at models/order.rb, models/campaign.rb and test/price_calculation_test.rb, and do your best to implement methods in price_calculation.rb; please do not modify files other than price_calculation.rb
5. The project is considered accomplished if all test cases pass.