Properties of Matter Part 3

A vessel with square cross-section and height of 6 m is vertically partitioned. A small window of 100cm2 with hinged door is fitted at a depth of 3 m in the partition wall. One part of the vessel is filled completely with water and the other side is filled with the liquid having density 1.5×103‌kg∕m3. What force one needs to apply on the hinged door so that it does not get opened?
(Acceleration due to gravity =10m∕ s2 )