When two resistance $\mathrm{R}_1$ and $\mathrm{R}_2$ connected in series and introduced into the left gap of a meter bridge and a resistance of $10 \Omega$ is introduced into the right gap, a null point is found at 60 cm from left side. When $\mathrm{R}_1$ and $\mathrm{R}_2$ are connected in parallel and introduced into the left gap, a resistance of $3 \Omega$ is introduced into the right-gap to get null point at 40 cm from left end. The product of $\mathrm{R}_1 \mathrm{R}_2$ is $\_\_\_\_$ $\Omega^2$