ANSWER IS D.
Process:
See in the attached fig,
BD=length of pole=?
AB=length of vertical(imagine)
BC=length of shadow=20 ft
In traingle ABC,
tan(36)=AB/BC
AB=tan(36)*20
AB=14.5308 ft
Now we find <BDC to use sine law.
For that,
<BDC+<DCB+<CBD=180
<BDC+36+(90+12)=180
<BDC=180-112-36
<BDC=42
Now we use sine law in traingle ABC,
BC/sin (<BDC) =BD/sin (<DCB)
20/sin(42)=BD/sin(36)
BD=(20*sin36)/sin42
BD=17.56=17.6(approx) >>>>>>>>ANSWER D
