Can you please answer this?

A weather balloon containing 600. L of He is released near the equator at 1.01 atm and 305K. It rises to a point where conditions are 0.489 atm and 218K and eventually lands in the northern hemisphere under conditions of 1.01 atm and 250K. if one-fourth of the helium leaked out during this journey, what is the volume (in L) of the balloon in landing.