an airplane maintains a speed of 630 km/h relative to the air it is flying through as it makes a trip to a city 750 km away to the north. (a) what time interval is required for the trip if the plane flies through a head- wind blowing at 35.0 km/h toward the south? (b) what time interval is required if there is a tailwind with the same speed? (c) what time interval is required if there is a crosswind blowing at 35.0 km/h to the east relative to the ground?