Pressure is force over area. So assuming your cube is at rest and on earth, then the force is mass x gravity and the pressure is mass x gravity / area.
A string quartet is made up of four musicians playing two violins, a viola, and a cello. These are all string instruments played either by plucking the strings or using a bow. The violins are the smallest and typically play the higher notes. The viola and cello are larger instruments and play the lower notes.
This new combination of two violins, viola, and cello was then adopted by composers of serious music, and from about 1750 the string quartet took its place as the principal medium for chamber music. Owing its development largely to the Austrian composer Joseph Haydn, it has reigned supreme to the present day.