A building is 1 ft from a 12​-ft fence that surrounds the property. A worker wants to wash a window in the building 1515 ft from the ground.ground. He plans to place a ladder over the fence so it rsts against the building.​ (See the​ figure.) He decides he should place the ladder 9 ft from the fence for stability. To the nearest tenth of a​ foot, how long a ladder will he​ need?