can any one help me ?

i have a homework and i did't find any answer for it

the question is

find the Domain , Range , matrix and the digraph for the relation R

a ) A = { 1,2,3,4,8 } = B , aRb if and only if a=b

b) A = { 1,2,3,4,6 } =B , aRb if and only if a multiple of b