Hel A seismologist places two recording devices 340 meters apart at points A and B. To check the calibration, an explosive is detonated between the devices 90 meters from point A. The seismologist notes the time the explosions register on the devices, and calculates the difference. The seismologist will detonate a second explosion east of point A. How far east should the second explosion be positioned so that the measured time difference is the same as for the first explosion?