Answer:
≈50.6
Step-by-step explanation:
Not sure what precision level this problem is looking for, but for right-skewed distributions, we know that the mean is going to be pulled right and therefore the mean should be larger than the median. To a high confidence level, the mean should fall between 50 and 59, or in the third column.
If a single estimation is wanted, assume the values inside each column are uniformly distributed: