A copper-nickel diffusion couple similar to that shown in Figure 5.1a is fashioned. After a 500-h heat treatment at 1000°C (1273 K) the concentration of Ni is 3.0 wt% at the 1.0-mm position within the copper. At what temperature should the diffusion couple be heated to produce this same concentration (i.e., 3.0 wt% Ni) at a 2.0-mm position after 500 h? The pre- exponential and activation energy for the dif- fusion of Ni in Cu are 2.7 X 10-4 m2/s and 236,000 J/mol, respectively.