Helium-neon lasers emit very high spectral purity red light at a wavelength of 632.8 nm, and were used in LaserDisc players and supermarket checkout barcode scanners. A large-cavity He-Ne laser has a volume of 0.785 L, and is filled with a mixture of 90.0% helium and 10.0% neon at a pressure of 1.00 torr. What is the mass of helium (in mg) in this laser at 25.0 °C? (760 torr = 1 atm)