7. (total 17 points) From the phase diagram of Pb-Mg alloy shown below,(a) (2 points) Identify the degree of freedom at the following points: A, B, C, D (a) (2

points) Identify the degree of freedom at the following points: A, B, C, D (b) (15 points) identify the following: phases, compositions (wt%), weight percent (wt%) of Phases and sketch microstructure (Label the phases in the microstructure). (1) At 75 wt% Pb- 25 wt% Mg, very slow cooling at the following temperatures: 600°C,500°C and 251°C (2) At 81 wt% Pb- 19 wt% Mg, very slow cooling at the following temperatures: 600°C,251°C and 100 °C (3) At 90 wt% Pb- 10 wt% Mg, very slow cooling at the following temperatures: 600°C,251°C and 249 °C