A diffusion couple is prepared using two hypothetical metals…

A diffusion couple is prepared using two hypothetical metals A and B. After a 20-h heat treatment at 800°C the concentration of B in A is 2.5 wt% at the 5.0-mm position within metal A. If another heat treatment is conducted on an identical diffusion couple, but at 1200°C for 20 h, at what position will the composition be 2.5 wt% B? Diffusivity of B in A is