Water is flowing in a trapezoidal channel at a rate of q = 20 m3/s. the critical depth y for such a channel must satisfy the equation 0=1-(q^2 b)/(ga_c^3 ) where g is gravity, ac is the cross-sectional area, and b is the width of the channel at the surface. for this case, the width and the cross-sectional area can be related to depth y by b = 3 + y and ac = 3y + 1/2y2. use initial guesses for the location of the root of a=0.5 and b= 2.5. the error on the solution should not exceed 1%.