A relation contains the ordered pairs (3,8) (6,10) (9,12), and (a, b). For which values of a and b is the relation a function

An unknown number x is at most 10. which graph best represents all the values of x? number line graph with closed circle on 10 and shading to the right. number line graph with open circle on 10 and shading to the right. number line graph with open circle on 10 and shading to the left. number line graph with closed circle on 10 and shading to the left.