Chemical Engineering - Stoichiometry - Discussion

Diffusion is that property by virtue of which a perfume bottle when opened up in a room, makes the whole room fragrant with its smell. If a perfume 'X' diffuses twice as fast as another perfume 'Y'; what is the molecular weight of 'Y', if the vapor density of gas 'X' is 2 ? Molecular weight of gas 'X' is to be assumed to be 2.