Answer: 10 days
Step-by-step explanation: It should be 10 days, I checked just to make sure. Here's the original reply I put before:
It's a fifth of the workers compared to before (2 now compared to 10 before). If 10 workers need 5 days, then 2 workers need 5 times that, so around 25 days, however that's considering they do 2 hours a day. The problem is that they do 5 hours now, so its 2.5 times more, so ideally they would take less time, meaning you divide 25 by 2.5, which gives 10 days.