It has been determined that the steady-state diffusion flux of a gas molecule through a solid metal plate is 5*10^-8 kg/m^2*s at a temperature of 1000K, and a concentration gradient of -300 kg/m^4. What concentration gradient is necessary to give a diffusion flux of 6*10^-8 at a temperature of 1300K if the activation energy for diffusion is 120,000 J/mol?