If a balloon holds 2000L of Helium at sea level, at 1 atm and 25 degress Celsius, what will its volume be if it is allowed to rise to a height og 8 miles, where the pressure is 0.30 atm and the temperature is -70 degress Celsius.

(P1V1/T1) = (P2V2/T2)

Remember T must be in kelvin.