The mode is the most common number. Here, it is 600 because it appears three times. I'm quite surprised you didn't know that, John.

For the rest of 2:

1. Just add up all of the numbers for each month.

2. Take your answer to 1) and divide it by 12 (the number of months)

3. Arrange the numbers in order and pick the middle one. Here, that is halfway between the 6th and 7th ones, so just take the mean of those.

4. As above, it is 600 because it is the most common.