heyy could you help me out with this question I have been stuck in this question??

Answer:
Choice A.
Step-by-step explanation:
tan < ABC = 60/40
So m < ABC = 56.31 degrees.
This makes m < DBC = 56.31 / 2 = 28.15 degrees
tan 28.15 = DC / 40
DC = 40 tan 28.15
= 21.407 ft.