4. The figure below is the equilibrium phase diagram of iron-carbon system. Assume a eutectoidaustenite steel with 0.77wt.% of carbon, and this austenite steel will completely transform topearlite steel if

decreasing the temperature along xx' to 727 °C and kept for sufficient longtime. The pearlite steel is a mixture of ferrite and cementite. Answer the questions below. (10') (1) Please calculate the fractions of ferrite and cementite in the pearlite steel. (Hint: Ferrite has 0.02 wt.% of carbon, Cementite has 6.67 wt.% of carbon).(2) Assume a hypo eutectoid austenite steel with 0.22 wt.% of carbon, and this hypo eutectoid steel will completely transform to the mixture of ferrite and cementite as well, if decreasing the temperature along yy’ to 727 °C and kept for sufficient long time. Calculate the fractions of ferrite and cementite in the formed mixture.(3) Compare the phase fractions in solution (1) with solution (2), explain why the eutectoid steel is stronger than the hypo eutectoid steel.