To determine the density of an object, which set of instruments would be ?

Ihave a density of 1.61g/cm^3 and a mass of 28g. find the missing value

An object is placed in front of a concave mirror between the pole and the focus of the mirror, what is the nature of the image formed by the mirror

Which of these best describes the term ecliptic? a. the circle where "earth meets the sky" b. the change in azimuth and altitude of an object c. the point directly above the geographic north pole d. the path of the sun through the constellations of the zodiac