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A diffusion couple is prepared using two hypothetical metals A and B. After a 20-h heat treatment at 800C the concentration of Bin 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 1000C for 20 h, at what position will the composition be 2.5 wt% B? Diffusivity of Bin A is 1.2 x 10-10 m/s and 1.11 x 10-9 m/s at 800C and 1000C, respectively. 0 - 10 mm O 5 mm 0 -15 mm 0 - 3 mm 0 - 20 mm O Insufficient information provided