A river catchment has a 2-hr UH with the ordinates 0, 3, 11, 35, 55, 66, 63, 40, 22, 9 and 2 m3/s. Assume the base flow at the time t = 0 hours is 50 m³/s and linearly increase to 74 m³/s. Compute the hydrograph resulting from two successive periods of effective rain of 2.0 cm and 3.0 cm respectively.