Which law states that the effect of pressure is the same for all portions of a confined fluid?

Two syringes of different cross-sections (without needles) filled with water are connected with a tightly fitted rubber tube filled with water. Diameters of the smaller piston and larger piston are $1.0 \; cm$ and $3.0 \; cm$ respectively.
$(a)$ Find the force exerted on the larger piston when a force of $10 \; N$ is applied to the smaller piston.
$(b)$ If the smaller piston is pushed in through $6.0 \; cm$,how much does the larger piston move out?

$A$ hydraulic lift as shown in the figure is used to lift a mass of $1000 \ kg$, which is placed on a piston $(P_1)$ of area $1 \ m^2$. If the cross-section area of the piston $(P_2)$ at the other end is $0.01 \ m^2$, then how much mass needs to be put on it to lift the $1000 \ kg$ (in $kg$)?

$A$ hydraulic automobile lift is designed to lift vehicles of mass $5000\,kg$. The area of cross-section of the cylinder carrying the load is $250\,cm^2$. The maximum pressure the smaller piston would have to bear is [Assume $g = 10\,m/s^2$].

In a vehicle lifter, the enclosed gas exerts a force $F$ on a small piston of $8 \text{ cm}$ diameter. The pressure is transmitted to a second piston of diameter $24 \text{ cm}$. If the mass of the vehicle to be lifted is $1400 \text{ kg}$, then $F$ must at least be $(g=10 \text{ ms}^{-2})$. (in $\text{ N}$)

In a hydraulic lift,the surface area of the input piston is $6 \ cm^2$ and that of the output piston is $1500 \ cm^2$. If $100 \ N$ force is applied to the input piston to raise the output piston by $20 \ cm$,then the work done is . . . . . . $kJ$.