Two separate bulbs contain ideal gases $\mathrm{A}$ and $\mathrm{B}$ at the same temperature. The molecular mass of $\mathrm{A}$ is half that of gas $\mathrm{B}$ and the density of gas $\mathrm{A}$ is twice that of gas $\mathrm{B}$ . The ratio of the pressure of $\mathrm{A}$ to that of gas $\mathrm{B}$ is