At an inn there are provisions sufficient for 20 days for 40 people. At the end of every 10 days 5 people leave off. How many days the provision will be sufficient for new?

At an inn there are provisions sufficient for 20 days for 40 people. At the end of every 10 days 5 people leave off. How many days the provision will be sufficient for new?

A. 20
B. 40
C. 30
D. none