Office challenge: Improve this Excel chart anyway you want

This week, impress your colleagues with your Excel charting skills! Improve this Excel chart based on default settings.

This week, the challenge is just for fun. The chart shown below is based on Excel chart default settings, and we all know that the default settings leave a bit to be desired. Your challenge is to improve the chart in any way you like. The only restriction is that you must work with the provided source values and you need to reflect all four series - but you can do so any way you please! For your convenience, you can download the sample worksheet.