A horizontal, galvanized iron pipe with a concentric annulus cross-section of inner diameter 0.3m and outer diameter 0.6m carries water that exits to the atmosphere and empties into a large reservoir of volume 100m3. If exit losses are negligible, estimate the time required to fill the tank if the pressure in the pipe at a section 10m upstream of the exit is measured as 5 times 10degree N/m2.