A 5-m-high, 5-m-wide rectangular plate blocks the end of a 4-m-deep freshwater channel, as...

A 5-m-high, 5-m-wide rectangular plate blocks the end of a 4-m-deep freshwater channel, as shown in Fig. P10-14. The plate is hinged about a horizontal axis along its unner edge through a point A and is restrained from opening by a fixed ridge at point B. Determine the force exerted on the plate by the ridge.