(a) A large-particle composite consisting of tungsten particles within a copper matrix is to be prepared. If the volume fractions of tungsten and copper are 0.70 and 0.30, respectively, estimate the lower limit for the specific stiffness of this composite, given the data as follows. Constituent Materials Cobalt Specific gravity Elastic modulus (GPa) 8.9 110 19.3 407 Nickel (b) How does the addition of a plasticizer influence the tensile strength of a polymer? Why?