Amaterial will float on the surface of a liquid if the material has a density less than that of the liquid. given that the density of water is approximately 1.0 g/ml, will a block of material having a volume of 1.2 x 10^4 in^3 and weighing 350 lb float or sink when placed in a reservoir of water?

You know the density o water, then find the density of the block. but remember to use the same system of measurements in both densities (I can see g/mL and in, lb in the same problem) use Metric System OR Standard System. 350 pounds divided by 1.20x10^4 cubic inches will give you density in standard system

Work done = force ×distancebut force = mass ×gravityand gravity = 10m\s force = 2×10 = 20 work done = 20×3 = 60 joules