(a) YMK structure copper has an atomic radius of 0.128 nm and an atomic weight of 63.5 g/mol. Calculate the theoretical density of copper. (b) Suppose that you work as an engineer in a factory. For high temperature work, you need to choose a durable material. The energy curves for these two materials are shown below. What material would you choose for this situation? Explain and compare the melting point, elasticity modulus and thermal expansion coefficients. (x-axis for interatomic seperation while y-axis for energy) Interatomic seperation r A B