Question

n(A)= 4,(B)=5,n(A*B)=

Answer 1

n(A)=4
n(B)=5
n(A*B)=5*4
=20

Answer 2

n(A)=4

n(B)=5

n(A*B)=mn

therefore,

n(A*B)=4*5=20

20 is the answer