Suppose your evil friend asks to borrow your ruby. You suspect your friend wants to steal your ruby and replace it with a worthless fake, so you find its mass on our commercial balance and obtain $30\mathrm{.}64g.$ When your friend returns what he says is your ruby, you find its mass and obtain $30\mathrm{.}76g.$

On the basis of this information, can you conclude that your friend has stolen your ruby? Explain your reasoning AND support your answer with a diagram like is used in the book.