Study the table below, which shows the average monthly rainfall (mm) for Aberystwyth.
| Month | Rainfall (mm) |
|---|---|
| Jan | 85 |
| Feb | 60 |
| March | 65 |
| April | 55 |
| May | 58 |
| June | 52 |
| July | 63 |
| Aug | 67 |
| Sept | 72 |
| Oct | 88 |
| Nov | 90 |
| Dec | 89 |
Calculate the mean of the rainfall values for Aberystwyth to two decimal places (2dp).
Show your working.