Three men are in a hot-air balloon. Soon, they find themselves lost in a canyon somewhere. One of the three men says, "I have an idea. We can call for help in this canyon and the echo will carry our voices far enough for someone to hear us." So he leans over the basket and yells out, "Helllloooooo! Where are we?" (They hear the echo several times.) 15 minutes later, the men in the balloon hear a..