Assume the altitude of a flying kite remains constant. As the length of rope, $k$, changes, the kite flies horizontally either toward the person holding the rope or away from the person. If $t$ represent time, are $\frac { d k } { d t }$ and $\frac { d x } { d t }$ positive or negative? Describe the way $\frac { d x } { d t }$ changes.