Let i represent a displacement 1 km due east and j represent a displacement 1 km due north. the control tower of an airport is at (0, 0). aircraft within 100 km of (0, 0) are visible on the radar screen at the control tower. at 12 : 00 noon an aircraft is 200 km east and 100 km north of the control tower. it is flying parallel to the vector b = -3i - j with a speed of 4010−−√ km h−1. at what time will the aircraft disappear from the radar screen