The mass curve of a rainfall event of 100 min duration over a catchment is given in the table.
| Time from start of rainfall (min) | 0 | 20 | 40 | 60 | 80 | 100 |
|---|
| Cumulative rainfall (cm) | 0 | 0.5 | 1.2 | 2.6 | 3.3 | 3.5 |
If the initial loss is 0.6 cm and φ-index is 0.6 cm/hour, the total surface runoff from the catchment is ______ cm (rounded off to one decimal place).