explain part c more

A tension test was performed on an aluminium alloy specimen. The resulting stress$$strain diagram is shown

in Figure $1\mathrm{.}1.$ Estimate:

$($a$)$ the proportional limit $($pl$)$

$($b$)$ the modulus of elasticity $($E$),$

$($c$)$ the yield strength $($y$)$ based on a $0\mathrm{.}2\%$ strain offset method $($see recommended textbook$),$

$($d$)$ the ultimate strength

$($e$)$ the stress at failure

$($f$)$ the modulus of resilience

$($g$)$ the modulus of toughnes