For a $0\mathrm{.}40$ wt$\%$ C iron$-$carbon alloy specimen, describe tempering heat treatments that would be required to produce water$-$quenched specimens having the following minimum yield$/$tensile strength$-$minimum ductility combinations. When entering the temperature ranges below, be sure to enter the lower temperature in the first box.

$($a$)$ tensile strength of $1200$ MPa, ductility of $15\%$EL

tempering must be carried out between

$($b$)$ yield strength of $950$ MPa, ductility of $55\%$RA

tempering must be carried out between

$($c$)$ tensile strength of $1500$ MPa, ductility of $35\%$RA

tempering must be carried out between

$($d$)$ yield strength of $800$ MPa, ductility of $20\%$EL

tempering must be carried out between

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