can anyone please help me with this?

question 1)

3 friends and 17 other boys are to be randomly divided into 5 teams of 4 players each.what is the probability that the 3 friends find themselves separated,each playing for a different team?

question 2)

an ordinary deck of 52 cards is shuffled.what is the probability that the top 4 cards have

a)different denominations?

b)different suits?

for ques 2,why cant i using the choosing method?

thx in advance!