Answer:
Mean
Step-by-step explanation:
Given

Required
Best measure of center
The mean is considered the best measure of center when there are no outliers in the given data.
Outlier is when a particular data set is far away from other datasets.
For instance: 20 is an outlier in the following data sets: 
Also, the given data are not open-ended.
An open-ended data is as follows: 
Since we do not have any of the above conditions, then the mean is the best center to use.