A watershed has 1.8 km2 of cultivated area, 2.2 km2 of forest land and 1.4 km2 of grassed area. The runoff coefficient of cultivated area, forest land and grassed area are 0.25, 0.15 and 0.30, respectively. The main drainage channel has a fall of 25 m in the total length of 2.5 km. The Intensity-Duration-Frequency relationship for the watershed is expressed as, I=70 T^{0.25}/(t_c + 15)^{0.4} where, I - intensity in cm h-1, T - recurrence interval in years and t_c - time of concentration in minutes. For a recurrence interval of 20 years, the peak rate of runoff for the watershed in m3 s-1 will be __________.