For a surface with outward$-$pointing normal, n$,$ and a direction, $,$ toward the light source, which expression below is always true when the light source is below the surface?

$nl0$

$nl=0$

$n*l<mn\; id="EditorElement\_12450302">0</mn>$

$n*l=0$

$n*l>0$

Note that $\backslash$times denotes the cross product and $$ denotes the dot product.