You have said that 15cm³ of gold weighs 2.8N. So I may infer that each cm³ of gold weighs about 0.19N. When I compare that figure with the 0.13N per cm³ of mercury, it becomes immediately apparent that the gold is more dense than mercury. Therefore, the sample of gold, no matter what its size or weight, will displace its total volume of mercury, and will go on to sink entirely beneath the waves in the mercury.
The answer and procedures of the exercise are attached in the following archives.
Step-by-step explanation:
You will find the procedures, formulas or necessary explanations in the archive attached below. If you have any question ask and I will aclare your doubts kindly.