Calculate the difference between the pressures inside and outside the flask.?

Sometimes it is difficult to be sure that the levels inside and outside a flask are actually equalized when collecting gas over water. If the the inside water level was 2mm lower than the outside water level. Given 1 mm Hg = 13.6 mm H20, density of water = 1 g/ml, density of Hg = 13.6 g/ml. Calculate the difference between the pressures inside and outside the flask.