Please provide solution and also present a derivation of the relation , i.e., the interdiffusion coefficient in terms of the second derivative of the Gibb's free energy (against concentration).

Assume interdiffusion proceeds in a binary diffusion couple according to parabolic law. Let X, (1) be a coordinate of Kirkendall plane at time 7, with respect to Matano plane (the initial interface) in the laboratory reference frame. Let v, (7) be a velocity of markers of Kirkendall plane, and with respect to Matano plane at the same moment of 7. Find the relation between X, vy, and 7