length $x$ changes. Find $A^{\text{'}}(12)m\frac{m^2}{m}m{A}^{\text{'}}(12)=,m\frac{m^2}{m}m$

Explain the meaning $of{A}^{\text{'}}(12)in$ the context $of$ this problem.

$A^{\text{'}}(12)$ represents the rate $at$ which the area $is$ increasing $asx$ reaches $24mm.$

$A^{\text{'}}(12)$ represents the rate $at$ which the area $is$ increasing with respect $to$ the side length $as$ A reaches $24m{m}^2.$

$A^{\text{'}}(12)$ represents the rate $at$ which the area $is$ increasing with respect $to$ the side length $asx$ reaches $12mm.$

$A^{\text{'}}(12)$ represents the rate $at$ which the side length $is$ increasing with respect $to$ the area $asx$ reaches $12mm.$

$A^{\text{'}}(12)$ represents the area $as$ the side length reaches $12mm.$