Solve the following problems and circle the right answer

A water jet of velocity $30\frac{m}{s}$ impinges normal to a stationery flat plate. The jet area is $4c{m}^2$ and the water density is $1000k\frac{g}{m^3}.$ The force required to hold the plate is:

A block of concrete weighs $200$ N in air and only $80$ N when immersed in fresh water $($density $1000k\frac{g}{m^3}).$ The block volume is:

$$

$3.$ The stability of a floating body is determined by:

$($a$)$ The location of center of gravity

$($b$)$ The magnitude of buoyancy force

$($c$)$ The line of action of the center of gravity

$($d$)$ The line of action of the buoyancy force