A conference attended by 200 delegates is held in a hall. The hall has 7 doors,marked A,B,......,G. At each door,an entry book is kept and the delegates entering through that door sign in it in the order in which they enter . If each delegate is free to enter any time and through any door he likes, how many different sets of seven lista would arise in all ? (Assume that every person signs only at his first entry) i) 206C6 ii) 199P5 iii) 199C5 iv) 206P6 plzzz xplain !!!!!!!!

A conference attended by 200 delegates is held in a hall. The hall has 7 doors,marked A,B,......,G. At each door,an entry book is kept and the delegates entering through that door sign in it in the order in which they enter . If each delegate is free to enter any time and through any door he likes, how many different sets of seven lista would arise in all ? (Assume that every person signs only at his first entry)

 

i) 206C6 ii) 199P5 iii) 199C5 iv) 206P6

 

plzzz xplain !!!!!!!!