A ladder 18 feet long is leaning against a wall that is perpendicular to level ground. The bottom of the ladder is 6 feet from the base of the wall. If the top of the ladder slips down 4 feet, how many feet will the bottom of the ladder slip?  Select the correct option
A) 12.5  B) 15  C) 18  D) 19  E) 25

Rationale: "18 ^ 2 - 6 ^ 2 = 288 it means that the height is equal to 16.9 . since the top of the ladder slips down 4 feet , then the height of the wall = 16.9 - 4 = 12.9 the bottom = sqrt ( 18 ^ 2 - 12.9 ^ 2 ) = sqrt ( 324 - 166.41 ) = 12.5 ans is a"
Answer: A