If aluminum is diffused into a thick slice of silicon with no previous aluminum in it at a…

If aluminum is diffused into a thick slice of silicon with no previous aluminum in it at a temperature of 1100°C for 6 h, what is the depth below the surface at which the concentration is 1016 atoms/cm3 if the surface concentration is 1018 atoms/cm3? D = 2 × 10_12 cm2/s for aluminum diffusing in silicon at 1100°C.