Rocky needs at least $32 to buy an amplifying speaker. he already has $17. which graph best represents all the possible dollar amounts that rocky can save to buy an amplifying speaker? a. number line graph with open circles on 0 and 15 and shading in between. b. number line graph with closed circles on 0 and 15 and shading in between. c. number line graph with closed circle on 15 and shading to the right. d. number line graph with open circle on 15 and shading to the right.