I am stuck on a kinetic energy problem, any help would be greatly appreciated:)))

Which changes of state do the labels represent? a: b: c:

Power can be defined as a. the distance over which work was done. b. how much work can be done in a given time. c. all the work in an given area. d. the energy required to do work.

An object weigh 40n in air ,weigh 20n when submerged in water,and 30n when submerged in a liquid of unknown liquid density.what is the density of unknown of liquid?