[填空题]
A helium-filled balloon escapes a child’s +mzlk3;x o8pu9bl3dlhand at sea level and 20.0 3zzn; 3g- hbyc bz9/ai$^{\circ} $ C. When it reaches an altitude of 3000 m, where the temperature is 5.0 $^{\circ} $ C and the pressure is only 0.70 atm, how will its volume compare to that at sea level? times the original volume