A vertical `U`-tube has two liquids `1` and `2`. The heights of liquids columns in both the limbs are `h` and `2h`, as shown in the figure. If the density of the liquid `1` is `2rho`.

a. Find the density of liquid `2`.
b. If we accelerate the tube towards right till the heights of liquid columns will be the same, find the acceleration of the tube.