Arescue helicopter is used to victims who fell in a ditch. the helicopter begins at sea level, which is an elevation of 0 feet. it then travels down for 100 seconds at a speed of 10.5 feet per second. it then travels directly up for 150 seconds at a speed of 5.2 feet per second. after this 250 second period, how much time, in seconds, will it take for the rescue helicopter to travel back to sea level at the helicopter's maximum speed of 15.8 feet per second?