A box culvert has a square-edged entrance (C. 0.6) and is 50 feet long with a slope of 1.0%. Determine the flow rate in the 6.5 feet by 6.5 feet concrete culvert if the headwater is limited to a depth of 13.3 feet above the invert (culvert bottom). Assume that the outlet is not submerged (i.e., hydraulic operation category (c)), but once the flow rate is found, verify that it is not category (b) by checking normal depth.