Runoff after rainfall

The parking lot of the Spenditall Megamall has an area of 128 ac. It is partially landscaped to provide some areas of grass. Assume that an average of 63% of the water that falls on the parking lot will flow into a nearby drainage ditch, and the rest either evaporates or soaks into unpaved areas. If as summer thunderstorm drops 3.23 cm of ran, how many cubic feet of water will flow into the drainage ditch?