A U-tube of base length “$l$” filled with same volume of two liquids of densities $\mathrm{\rho }$ and 2$\mathrm{\rho }$ is moving with an acceleration “a” on the horizontal plane as shown in the figure. If the height difference between the two surfaces (open to atmosphere) becomes zero, then the height h is given by $\frac{\mathrm{xa}l}{2\mathrm{g}}$ then $\mathrm{x}$ will be