Answer:
1. 5P2 you'll get 20
2.a.10P6 = 151200
b.10P4= 5040
3.a. C(2,0)=1+C(2,1)=2+C(2,2)=1
a.=4
b.C(10,2)=45+C(11,3)=165
b.= 210
