If temperature is steady, then atmospheric pressure P (inpounds/square inch) differs with altitude above sea level h in accordance with law P=p0e^-kh where p0 is atmospherice pressure at sea level & k is constant. If atmospheric pressure is 16 lb/in^2 at sea level and 11.5lb/in^2 at 3000 ft, determine atmospheric pressure at altitude of 9000 ft.