Task: Question Answering
Input (English): Problem: 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 ? 
Options: a ) 12.5 , b ) 15 , c ) 18 , d ) 19 , e ) 25
Output (English): a