<image> Cyclists A and B are training on the same straight road. They start at the same time, from the same place, and head in the same direction. During the ride, cyclist B changes speed once. The graphs of the distance $$y$$ (in kilometers) traveled by each cyclist with respect to time $$x$$ (in hours) $$(0\leqslant x\leqslant 4)$$ are shown in the figure. 
$$(1)$$ Find the speed of cyclist A.
$$(2)$$ Find the function expression corresponding to line $$AB$$.
$$(3)$$ Directly state the value of $$x$$ when the distance between cyclists A and B is $$5$$ kilometers.