Some hypothetical alloy is composed of 12. 5 wt% of metal a and 87. 5 wt% of metal b. If the densities of metals a and b are 4. 27 and 6. 35 g/cm3, respectively, whereas their respective atomic weights are 61. 4 and 125. 7 g/mol, determine whether the crystal structure for this alloy is simple cubic, face-centered cubic, or body-centered cubic. Assume a unit cell edge length of 0. 395 nm.