A fire hose passes over the edge of a 15-ft vertical retaining wall and is being reeled in on level ground on the opposite side of the wall. The portion of hose outside the wall forms a straight segment from the top of the wall to the reel. If the hose is being pulled in at a constant rate of 3 ft/s, how fast is the reel moving horizontally toward the wall at the instant when 25 ft of hose remain outside the wall?
a) 3.75 ft/s
b) −3.00 ft/s
c) −3.75 ft/s
d) −2.40 ft/s