The shape of the tunnel is represented by the downward parabola equation y = -x^2 +3. The parabola has a vertex at elevation y== 3. First, we need to determine the bottom elevation of the tunnel y, where x = 7/2 = 3.5 m. It is easy to do: = -(3.5)^2 + 3 = -12.25 + 3 = -9.25 m. Now, the height of the tunnel is the difference of two elevations H = - = 3 - (-9.25) = 12.25 m. ANSWER