The old Diefunbunker near Ottawa has two Identical air-raid sirens 5 meters apart horizontally and producing sound in phase at 275Hz. An observer is 1.0 km away on a line at 45 degrees to the line joining the sirens. What is the SHORTEST distance in meters she must walk (in any direction) to get to a location where there is no sound, due to destructive interference? The velocity of the sound is 350m/s.