The figure shows a U-tube having a $5 \: mm \times 5 mm$ square cross-section filled with mercury (specific gravity  $13.6$) up to a height of $20$ cm in each limb (open to atmosphere)

If $5 \: cm^3$ of water is added to the right limb, the new height (in cm, up to two decimal places) of mercury in the LEFT limb will be ________