An emergency rescue craft in the form of a spherical balloon of radius 3.00 m holds a number of survivors after their ship sinks in the mid Atlantic. Prior to inflation, the mass of the compressed rescue craft was 40.0 kg. If the rescue craft is half submerged - that is, the top hemisphere is still visible above the waterline - what is the mass of the men inside? Assume the volume of the men is negligible compared with the volume of the air in the rescue craft, which also must be included in the calculation. Assume the density of salt water is 1025 kg/m3.