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Solution : It must be clear from then diagram. The equation of the parabola = $y = -bx^2$
Find b,
Now using b evaluate Y1 at x = 80 and you will see te clearance available is only 28.8 which is less than the 60 m required for the barge to travel to the right and allow two way traffic
Now using b evaluate Y2 at x = 40 and you will see the clearance available is 67.2 m which is more than the 60 m required for the barge to travel in the center.
Thanks
Satish