15 people working 5 hourse per day can make 30 units of a product in 10 days. Assuming all other factors remaining constant and people of same efficiency are used to make the same products, in how many days can 10 people make 10 units of the product if each of them works 10 hours per day?

- 2.5 days
- 7.5 days
- 12 days
- 26 days