Find BD
Remember soh-cah-toa?
opposite/adjacent
tan30=400/x
xtan30=400
x = 400/tan30
Find BC
Still toa. . . still toa
90 + 60 = 150
180-150 = 30
BAC = 30
tan30=x/400
400tan30=x
BD-BC=CD
If you followed my steps, your answer should come to you.
If you didn't and are a lazy pr*ck who relies on others to do their semester exam problems for them, the answer is A. Or 461.