I need help with this question I don't understand.

A woman (at point A) on top of a 450-foot-high building spots a helicopter (at point B). As she views the helicopter, its angle of elevation is 35 degrees. At the same instant, at the ground level entrance to the building (directly below the woman at point C) the angle of elevation to the helicopter is 65 degrees. How high is the helicopter above ground level? B A $35 Building