The temperature of 2.0 g of helium is increased at constant volume by ΔT. What mass of oxygen can have its temperature increased by the same amount at constant volume using the same amount of heat?

I know for constant volume I should use the equation: Q=mCsubvdeltaT

I also know that in my book Molar specific heats of gases (J/mol*K) at 20degrees Celcius:

Csubv of Helium = 12.5
Csubv of Oxygen = 20.9

How do I set up this equation and solve it?