Jake wants to determine the density of a small chocolate bar that has a rectangular shape. He has a ruler, and a scale/balance. He measured the mass of the chocolate bar, but does not remember what units he should express the mass in. What unit is correct

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point