A man lives on the 10th floor of an apartment building. Every morning he takes the elevator (lift) all the way down to the bottom and goes to work. In the evening, when he comes back from work, he gets into the elevator(lift), and if there is someone else in it, he goes back to the 10th floor. On rainy days he also goes directly to his floor. On all other days, he goes to the 7th floor and walks up 3 flights of stairs to his apartment (flat). Why?
