The wear resistance of a steel shaft is to be improved by nitrogen hardening of its surface. The initial nitrogen content of steel is 0.002wt%, whereas the surface concentration during heat treatment is maintained at 0.50wt%. A nitrogen content of 0.1wt% is desired at a position of 0.40-mm below the surface a.) Determine the diffusion time required at 600°C. The pre-exponential and activation energy for diffusion of nitrogen in steel is given as 3X10^-7 m²/s and 76.15KJ/mol, respectively. b.) What time will be required at 500°C to produce the same resul (in terms of concentration at a specific depth) as for 10-hours at 600°C?