The activation energy for self$-$diffusion in material A and $B$ are $31,300ca\frac{l}{m}ol$ and $41,000$ respectively. Material A creeps at $0\mathrm{.}003i\frac{n}{i}\frac{n}{h}$ while material B creeps at $0\mathrm{.}001i\frac{n}{i}\frac{n}{h}$ when a stress of $18,000$ is applied at $681C.$ If the creep rate of these materials are dependent on self$-$diffusion, compare the creep rate of each materials at $900C$