A balloon is filled with helium at sea level. The volume was measured to be 3.1 liters at a pressure of 0.97 atm. If the balloon is released, it drifts upward. At a height of 4 kilometers, the pressure is measured to be 0.61 atm. What is the new volume of the balloon?

5.0 L
0.19 L
4.9 L
1.9 L