Chem 1 honors help!?

A hot-air balloonist is concerned about his upcoming flight, and decides to do a simple chemical calculation. He knows that his balloon contains 1548 L of Helium gas, on the ground where the temperature is 15oC and the pressure is 1013 mbar. When he ascends to an altitude of 1.5 km, the pressure is 845.6 mbar and the temperature is 5.25 oC. What is the volume (in liters) of the ascended balloon?