Chemistry, calculating densities

*'In an experiment, a student was asked to measure the densities of liquid acetone and metallic chromium. He was given a pycnometer which weighed 26.880 g empty. When filled with water and stoppered, the mass was recorded as 54.992g at 28°C. The pycnometer was cleaned and filled with acetone. The mass was 49.137 g. Again, the flask was cleaned and dried. Into it were added some chunks of chromium and the total was found to weight 78.666 g. Leaving the chromium in the pycnometer, it was then filled with acetone. The flask, metal and acetone was found to weigh 95.199 g. From this data, calculate the density of acetone and the density of chromium (show all your calculations). '*

The answer is meant to be in g/mL, and I have to admit I am a bit lost. These are the steps I think need to be taken: 1) find the volume of the empty pycnometer. 2) find the density of the acetone. 3) Find the volume of the chromium. 4) Find the density of the chromium. I guess the main thig I am confused with is how to use the numbers and where?