=exp(2Dt/I2) where is the residual segregation index of the alloy element; D is its diffusion coefficient; t is time; and I is the band-spacing. Before homogenization the "banding" has a spacing of 20m with maximum and minimum concentrations of 8 wt.\% and 0.4 wt.\%, respectively. At 1200C, D=1015m2/s; at 1250C,D=61015m2/s. (a) Homogenization is carried out at 1200C for 5 hrs. Calculate the residual segregation index. (b) To further reduce the residual segregation index, the alloy is subjected to additional homogenization at 1250C for another 5hrs. Calculate the residual segregation index after the two-step treatment