The measure of center that best represents the data is median because the data is ordinal, that is it is in ranks. The first is 21, the second is 34, third is 56, fourth is 57 and fifth is 58.
You first do 432 divided by 9 which is 48. However, there could be multiple dimensions for the base because 48 is a composite number. One example could be 6 by 8
