A spherical hot-air balloon is initially filled with air at 120 kPa and 35oC with an initial diameter of 3 m. Air enters this balloon at 120 kPa and 35oC with a velocity of 2 m/s through a 1-m diameter opening. How many minutes will it take to inflate this balloon to a 15-m diameter when the pressure and temperature of the air in the balloon remain the same as the air entering the balloon?