Consider a copper-nickel (Cu-Ni) couple similar to the one shown in Fig. 6.1a in the book. This couple was held at about 975oC for 20 days resulting in a concentration of Ni of 2.8 wt% at a depth of 1.2 mm within the Cu. At what temperature should the diffusion couple be heated to and held for 20 days to produce a concentration of 2.8 wt% Ni at a depth of 2.2 mm within the Cu. For the diffusion of Ni in Cu use D0 and Qd values of 0.00025 m2/s and 245 kJ/mol respectively.