Problema $9\mathrm{.}58+9\mathrm{.}59($Chin edited$)$ A proposed $20-$ha development includes $5$ ha of parking lots, $90$ ha of buildings, and $55$ ha of grassed area with type $A_1$ soiling good condition. Runoff from the parking lots and buildings are both routed directly to grassed areas before leaving the area.

a$)$ Estimate the runoff from the site for a $200$ mm rainfall event.

b$)$ Consider the case of the runoff from the buildings, especially the roofs, is discharged directly to the parking lots and then to the pervious areas. Based on this result, what can you infer about the importance of directing roof drains to pervious areas?

c$)$ Repeat part $($a$)$ using the area weighted curve number. How would your result change if the roof drains were directly connected to the parking lot?