1. An airplane starts at 0 feet. It rose 21,000 feet at takeoff. it then descended 4,329 feet because of clouds. An oncoming plane was approaching, so it rose 6,333 feet. After the oncoming plane passed, it descended 8,453 feet, at what altitude was the plane flying? 2. From the top of a mountain to the floor of the valley below is 4,392 feet. If the valley is 93 feet below sea level, what is the height of the mountain?