The semiconductor alloys of gallium arsenide (gaas) and gallium phosphide (gap) are used to make red, yellow and orange light-emitting diodes. both gaas and gap have the zinc blende crystal structure and are soluble in one another at all concentrations. determine the concentration in weight percent of gap that must be added to gaas to yield a unit cell edge length of 0.5570 nm. the densities of gaas and gap are 5.316 and 4.130 g=cm3, respectively.