(a) The sets A={2,4,6} and B={x,y,z}. Which of the following expres- sions (if any) are valid relations from A onto B? Explain your rea- soning. i. {(2, ), (4, ), (4,2), (6, 2)} ii. {} iii. {(2, x)} iv. {(2, x) , (4, ), (6, )} (b) The set A = {2, 3, 4, 5, 6, 7, 8, 9, 10,12}. R is a relation on A defined by R = {(a, b) : a a A, b E A, a is a multiple of b}. Write out the elements of R.