Let vec$(F)=(2a^{2}x8a{y}^2)vec(i)(8z^3-1ay)vec(j)-(z8x^{2}8y^2)vec(k).$

$($a$)$ Find the value$($s$)$ of a making divvec$(F)=0$

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$($Enter your value, or if you have more than one, enter a comma$-$separated list of your values.$)$

$($b$)$ Find the value$($s$)$ of a making divvec$(F)$ a minimum

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$($Enter your value, or if you have more than one, enter a comma$-$separated list of your values.$)$