Calculate Mass of Balloon with PV=mRT

[GoSS190]

Homework Statement

A balloon contains 6000m^3 of helium at 28 degrees C. and 99kPa absolute. Just before launch determine the mass of the balloon.

Homework Equations

Determine the mass of the balloon.

The Attempt at a Solution

I think you might have to use PV=mRT but I am not sure about how you would get R really. Any thoughts? Is that the right equation to use here?

 

[uradnky]

R = 8.314 / Molecular Weight of helium