permutation and combination

1. nancy has bought 10 different presents. in how many ways can she
a)divide the presents inti 5 groups of 2?
b)give all the presents to 2 friends such that each of her friends receives at least 3 present?

2. there are 4 black marbles and 4 white marbles in a bag. 2 points will be awarded if a black marble is drawn and 1 point will be awarded if a white marble is drawn. if 4 marbles are drawn, find the no. of ways to obtain at least 6 points.

3.a 5-card poker hand is selected from a deck of 52 playing card. how many fidderent poker hands
a)contain excatly 1 king
b)contain at least 1 king
c)contain excatly 1 pair

ans:
1a)945
1b)912
2)11
3a)778320
3b)886656
3c)1098240