A direct runoff hydrograph due to an isolated storm with an effective rainfall of 2 cm was trapezoidal in shape as shown in the below figure. The hydrograph corresponds to a catchment area (in sq. km) of

The parameters in Horton's infiltration equation are given as, f_{o} = 7.62 cm/hour, f_{c} = 1.34 cm/hour and k = 4.182/hour. For assumed continuous ponding the cumulative infiltration at the end of 2 hours is