Rainfall intensities in $$\frac{mm}{hr}$$ at half an hour interval during a 4-hour storm were :
5,9,20,13,6,8,16 and 3 $$\frac{mm}{hr}$$.If the corressponding observed runoff is 27.45 millions $$m^{3}$$ from a basin having an area of 1830 $$km^{2}$$? The $$\phi$$ index of the storm is

A

6.25 $$\frac{mm}{hr}$$

B

6.7 $$\frac{mm}{hr}$$

C

7.2 $$\frac{mm}{hr}$$

D

7 $$\frac{mm}{hr}$$