A flow of 1,650 m3 /s flows in a channel with the following characteristics: B=b=30 m; y0=2.80 m; n=0.018. In a section "B" of the channel, the discharge is yB=3.50 m: a) Identify the profile explaining your reasoning (type of profile, control section) b) Calculate the position of the discharge "yB" upstream of the section, such that the velocity in both sections differs by 10% (finite increment method, use increments or decrements as the case may be, equal to 0.10 m in the discharge).