Consider the following TTT diagram for the FeFe3C system. Starting from austenite above 800C, which of these heat treatments would lead to 50% pearlite and 50% bainite? (a) Cool to 600C and hold for 8s, cool to 400C and hold for 1000s, then quench. (b) Cool to 590C and hold for 8s, then quench. (c) Cool to 620C and hold for 100s, cool to 400C and hold for 1000s, then quench. (d) Cool to 700C and hold for 50s, then quench