A) There are 18 students pursuing major in Physics and 7 students in Computer Science major. In How many ways two representatives be selected so that one is a Physics and one is a Computer major.

B) There are 13 students pursuing major in Physics and 8 students in Computer Science major. In How many ways a representative be selected so that one is a Physics or one is a Computer major.

C) A shoe manufacturing company makes shoes in three colors (pink, blue and black), four sizes (S, M, L, XL) , for 5 purposes ( basketball, soccer, walking, running and hiking). How many different types of shoes are manufactured.

D) what is the value of 6C4

E) what is the value of 3C1

F) what is the value of 4C2

G) what is the value of 5C1

H) what is the value of P ( 3, 2 )

I) what is the value of P ( 5, 3)

J) what is the value of P (7, 4)

K) what is the value of P ( 2, 1)

L) what is the value of P ( 4, 2 )

M) what is the value of 1C1

N) 0!

O) 1!