9. Your boss wants to consider hardening only the outer 0.05mm thick layer of a 1040 steel material at 700C, so that the inner layer is unchanged in hardness. Determine a) how long will it take to do this if you assume that 0.05mm is the depth of the tail and can be modeled according to x=4.6(Dt)1/2 b) at what depth from the surface will the carbon concentration be 0.52 of the initial value, for the time in (a) for the 1040 steel. You may assume that the C profile obeys an error function relationship where c/co=erf(z)