A sample of N2 gas is contaminated with a gas (A) of unknown molar m...calculate molar m....?

A sample of N2 gas is contaminated with a gas (A) of unknown molar m. The partial pressure of each gas is known to be 200. torr at 25oC. The gases are allowed to effuse through a pinhole, and it is found that gas A escapes at 2 times the rate of N2. How do I find the molar m of gas A? Is it even possible?