Consider a ladder 5 meters tall, and a 150 kg weight on top of it. The ladder is leaning against the wall.

Consider a ladder 5 meters tall, and a 150 kg weight on top of it. The ladder is leaning against the wall. The friction between the ladder and both the wall and the floor is negligible, and the ladder is prevented from sliding by a horizontal force applied to the bottom of the ladder. Which angle between the ladder and the wall require the lowest force to keep the weight up above the ground?