p空气gV=（50kg+p气V）g,V=50kg／（p空气－p气）,空气密度为1.293g/L,即p空气=1.293g/L,p氦气=0.1786g/L,p氨气=0.7081g/L .计算得V氦气=44867.2L,V氨气=85484.7L.