Achilles is lurking inside a high wall that defends an ancient city. At his location, it is 10 meter thick and 25 meter high. An enemy archer wishes to hit Achilles with his arrow. He can fire his arrows at 50 meter per second, and he is crouching 27 meter from the outside of the city wall. The release point of the arrow and its landing height are both at ground level.
(a) If Achilles stands up against the inside surface of the wall he will be safe. If he begins to walk away from the wall, find at what distance from it will the archer be able to hit him?
(b) Xena is inside the city, very far from the wall, and she is also safe. Suppose Xena starts walking toward the wall. Find at what distance from the inside surface of the wall will she no longer be safe?