Give conditions on the constants $a$, $b$ and $c$ that ensure that the flux integral $\int_S \vec F\cdot d\vec S$, where $\vec F=a\vec i +b\vec j+c\vec k$ and $S$ is the upper half of the unit sphere centered at the origin and oriented downward, is positive.

(For each, if there is no restriction on the constant select = and enter anything for the value.)
$a$ ? < <= = >= >
$b$ ? < <= = >= >
$c$ ? < <= = >= >