A heat engine using a monatomic gas follows the cycle shown in the figure.

$($A$)$ Find $W,Q,$ and $E_{th}$ for the process $12.$

$W_{12}=J,Q_{12}=J,E_{12}=J.$

$($B$)$ Find $W,Q,$ and $E_{th}$ for the process $23.$

$W_{23}=J,Q_{23}=J,E_{23}=J.$

$($C$)$ Find $W,Q,$ and $E_{th}$ for the process $31.$

$W_{31}=J,Q_{31}=J,E_{31}=J.$

$($D$)$ What is the thermal efficiency of this heat engine?

$e=,\%.$