Explanation:
Let's assume that you work all 52 weeks in a year. In other words, you either have no time off, or you get paid vacations and paid sick leave.
If this is the case, then you earn 125*52 = 6500 dollars per year. This doubles to $13,000 total over the course of the two year period. Take 20% of this to get the final answer.
20% of 13000 = 0.20*13000 = 2600