An asphalt pavement drains into a rectangular concrete channel. The catchment surface has an average slope of 1.0%, and the distance from the catchment boundary to the drain is 30 m. The drainage channel is 60 m long, 20 cm wide, and 25 cm deep, and has a slope of 0.6%. For an effective rainfall rate of 50 mm/h, the flowrate in the channel is estimated to be 0.02 m ³ /s. The Manning n for an asphalt surface is 0.011 and for a concrete surface is 0.013. Estimate the time of concentration of overland flow for the catchment and estimate the time of concentration for the drainage channel.