A manually cleaned bar screen has bars with a thickness of 8-mm (0.31-in) and openings 25-mm (0.98-in). After operating for a period of time, assume that the opening size decreases to 10-mm due to the accumulation of materials (debris) on the screens. If the approach velocity is 0.68 m/s (2.3 ft/s), determine if the screen needs to be cleaned. Why or why not?