A 100 ac. the watershed consists of parking lots (30%), roofs (15%), green lawns with moderate slopes, clay/silty soil (50%), and concrete sidewalks (5%). The IDF for the area is given. A concrete sewer is to carry the above runoff at a velocity of 2 fps to be self-cleansing and at most 8 ft/s to prevent erosion. If a 25-year storm lasts for 1 hour: 

a) Calculate the peak runoff (cfs)

b) Is a 5-ft-diameter concrete sewer adequate to carry this runoff when flowing (a) full and (b) half-full? 

c) Specify a square-shaped sewer that will carry this runoff while flowing half-full.