A trapezoidal channel is designed to carry a discharge of 1800 cfs at normal depth on a slope of XXXXXXXXXXft/ft. The side slopes of the channel must be 1.5 H/ 1 V and the Manning n value is...

A trapezoidal channel is designed to carry a discharge of 1800 cfs at normal depth on a slope of 0.0005 ft/ft. The side slopes of the channel must be 1.5 H/ 1 V and the Manning n value is 0.035. If the channel is to be a regular earthen canal in good condition, what should be its dimensions for maximum hydraulic efficiency?