Adiffusion couple of two metals, a and b, was fashioned as shown in figure 5.1. after a 26 hour heat treatment at 1050°c (and subsequent cooling to room temperature) the concentration of a is 4.0 wt% at the 14-mm position within metal b. if another heat treatment is conducted on an identical diffusion couple, only at 711°c for 26 hours, at what position (in mm) will the composition be 4.0 wt% a? the preexponential and activation energy values for the diffusion of a in b are 2.4 × 10-4 m2/s and 154 kj/mol, respectively.