A piece of 0.1% C steel is to be carburized at 930C until the carbon content is raised to 0.45% C at a depth of 0.020 in. (0.050 cm). The carburizing gas holds the surface composition at 1% carbon for all t > 0. If D=1.4 x 10^-7 cm^2/sec: (a) Calculate the time required at the carburizing temperature. (b) What time is required at the same temperature to double this amount of penetration? (c) If D=0.25 exp(-34,500/RT) cm^2/sec, what temperature is required to get 0.45% C at 0.040 in. (0.10 cm) in the same time as 0.02 in. was attained at 930C?