Three friends, A, B, and C form the vertices (corners) of a triangle on flat ground. Friend “A” is standing directly at the bottom of a sheer cliff. Directly above A, at
the top of the cliff, a fourth friend, “D”, is standing. The distance on the ground
between B and C is 400 m. The angle at “C” between A and B is 35º. The angle
at “B” between A and C is 27º. The angle of elevation from “C” to “D” at the top
of the cliff is 18° Find the angle formed at “D” between “B” and “C”.