A triangular shaped direct runoff hydrograph of a storm is obtained from a catchment with an area of 40 km 2. If. the base period and the peak flow rate are given as 60 hours and 20 m 3 /s, respectively, then the rainfall excess that has resulted the above hydrograph should be ______________

A

4.8 cm

B

5.4 cm

C

6.2 cm

D

6.8 cm