How do I calculate average margin provided I have the following data:

Sales(litres)
John 15 000
Mark 20 000
Peter 10 000

Target margin

John 0.5
Mark 0.2
Peter 0.3

Gross profit

John 500
Mark 600
Peter 200

Given that this is out of context, I'm not sure what they are looking for. A "target margin" doesn't mean that's the actual margin. So does that have anything to do with it? Is it a weighted average based on those percentages? I really don't know what they want.