An 8-hour storm with incremental rainfall during each successive hour is tabulated herewith. What will be the correction to total runoff when, whereas the actual ϕ index was 0.5 cm/hour, a wrong magnitude of 0.6 cm/hour was adopted in computing the total runoff?

Time from start (hour)	Incremental rainfall in each hour (cm)
1	0.4
2	0.8
3	1.2
4	0.9
5	1.8
6	1.0
7	0.3
8	0.8