A military unit prepares rice for 30 people to eat in 15 days, the amount of food each person in a day is the same. After eating for 3 days, 10 people moved to another place. Ask in how many days does that unit eat the remaining rice?

Question 4: A military unit prepares rice for 30 people to eat in 15 days, the amount of food each person in a day is the same. After eating for 3 days, 10 people moved to another place. Ask in how many days does that unit eat the remaining rice?