physics
posted by anonymous .
A metal container, which has a mass of 9.4 kg contains 14.2 kg of water. A 1.7kg piece of the same metal, initially at a temperature of 160.0°C, is dropped into the water. The container and the water initially have a temperature of 15.0°C and the final temperature of the entire system is 17.0°C. Calculate the specific heat of the metal.
I got 124.73 but when I put units in it says it's wrong. What are the units? Please help. Units always confuse me.

ΔQ1 + ΔQ2 = ΔQ3,
c• m1•ΔT1 +ñ(w) •m2• ΔT1 = c• m3•ΔT2,
ñ(w) •m2• ΔT1 = c• (m3•ΔT2  m1•ΔT1),
c = {ñ(w) •m2• ΔT1}/{m3•ΔT2  m1•ΔT1} =
=4180•14.2•2/(143•1.7 – 9.4•2) = 530.5 J. 
Expiain why a piece of wood floats in water?