Use 30 marines with stimpack to defeat as many banelings as possible.
win condition: time elapse (120 seconds)
defeat condition: all marines are dead.
baneling defeat reward: for each baneling defeated, score increase by 1. if all banelings are defeated, you will get full health for remain marines with extra 15 marines.
hint: try spit marines and hit&run. https://www.youtube.com/watch?v=JBxHTfMhxIs