To answer this question we will use the following diagram as a reference:
Recall that in a right triangle we get:
[tex]\tan\theta=\frac{OppositeLeg}{AdjacentLeg}.[/tex]From the given diagram we get:
[tex]\tan39º=\frac{SB}{OS}=\frac{SB}{500ft.}[/tex]Therefore:
[tex]SB=500ft\tan39º.[/tex]Simplifying the above result we get:
[tex]SB\approx404.89ft.[/tex]Answer: 404.89ft.