Following is tabulated data that were gathered from a series of Charpy impact tests on a ductile cast iron.

(a) Plot the data as impact energy versus temperature.

(b) Determine a ductile-to-brittle transition temperature as that temperature corresponding to the average of the maximum and minimum impact energies.

(c) Determine a ductile-to-brittle transition temperature as that temperature at which the impact energy is 80 J.

Impact Energy (J) Temperature (C) -25 124 -50 123 -75 115 -85 100 -100 73 -110 52 26 -125 -150 9 -175