A trapezoidal channel is to be excavated at a site where permit restrictions require that the channel have a bottom width of 5-m, side slope of 1.5:1 (H:V), and a depth of flow of 1.8-m. If the soil material erodes when the shear stress,, on the perimeter of channel exceeds 3.5-Pa, determine the appropriate longitudinal slope and corresponding flow capacity of the channel. Use Darcy-Weisbach equation, and assume that the excavated channel has an equivalent sand roughness of 3.0-mm