A truck has to pass under an overhead parabolic arc bridge which has a span of 20 meters and is 16 meters high. If the tank is 14 meters wide, is placed in the truck with its sides vertical, and the top of the tank is 7.5 meters above the street level, what is the smallest clearance from the top of the tank so that the truck can pass under the bridge?

A truck has to pass under an overhead parabolic arc bridge which has a span of 20 meters and is 16 meters high. If the tank is 14 meters wide, is placed in the truck with its sides vertical, and the top of the tank is 7.5 meters above the street level, what is the smallest clearance from the top of the tank so that the truck can pass under the bridge?