A. A tall roller with a 12.0 cm2 cross section is partly filled with mercury, the free surface of which is 5.00 cm above the bottom of the cylinder. Above mercury, water is slowly poured and the two fluids are not mixed. What volume of water should be added to double the differential pressure at the bottom of the cylinder? (Given for water pw = 1,0 × 103 Kg / m3, for mercury ρHg = 13,6 × 103 Kg / m3)

B. A short circuit interrupts any power supply to a diving vessel located 30 m below the ocean surface. The crew to escape has to open a buckart on the base, 0.75 m2 and weighing 300 N. If the internal pressure is 1.0 atm, how much downward force should they exert to open the door? Based on the value of the power you find, consider whether it is humanly possible to open the bucket. (Given for seawater ρ = 1.03 × 103 Kg / m3 and g = 9.80 m / s2)